Shield Block mechanics - Blocking for Blockheads
Shield blocks reduce physical dmg taken, obviously. But what determines how often you block? Or how much damage is reduced?
Block rates - Now with 0.215 apr!
Block rate factors.
-Player shield skill.
-Attacker combat skill
-Shield size.
These three factors determine your base block rate versus an enemy. That's it. Anything else has nothing to do with it. (I was hella surprised when I figured out player level didn't matter.)
There are two more ways to adjust block rate from the base. These are
-Block chance+ gear.
-JA/Spell modifiers(Reprisal/Palisade)
While we know the factors involved we don't really have a solid block rate formula. There's been a lot of testing and mathing, but we still don't have a complete model.
What we do know is that shield skill and attacker combat skill are compared, and then converted to blockrate. This value, whether positive or negative is used to adjust the base block rate derived from the shield size.
Shield size is a value found only in the DATs for items. Nothing in game actually references the numbers directly.
Size 1 are bucklers.
Size 2. Round shields.
Size 3. Kite shields.
Size 4. Tower shields
Sizes 5 and 6 are rather unique. There are only 2 size 5 shields and one size 6.
We don't know a lot about the base block rates of the various shield sizes. It very difficult to tell the effects of the base rate from the effects of your shield skill.
The rumors go, Sizes 1 through 4. 1 having the highest block rate(of these 4 sizes!) and 4 having the lowest. Their damage reduction works in reverse, with size 1 having the lowest and 4 the highest(again, of these 4 sizes.)
Size 3 was generally considered the ideal balance of block rate and dmg reduction, before the introduction of Aegis. This still sorta holds when looking at new shields.
Sizes 5 and 6 don't play along with the system 1~4 seem to use.
Size 5 (Aegis/Srivatsa) has 5% more base block rate and base block damage reduction than a size 3 shield.
Size 6 (Ochain only)has 10% lower dmg reduction than a size 3(40% base) but has massively higher base block rate. Size 6 has about a 65 block rate advantage over size 3.
Block chance+ gear
Not too much to say here. +1 block chance adds +1% block rate.
It is notable how this gear interacts with Reprisal though. I'll go over this in the Reprisal section though.
Reprisal
Our dear friend reprisal. Making shields so much more fun.
Reprisal modifies your current block rate by * 1.5, or * 3.0 with Priwen(effect bonus is lost if priwen is removed)
It's important to note that because Reprisal modifies your current block rate the gains from Reprisal can be large or pitiful, depending on your current block rate. If you have a 5% block rate, reprisal is only going to add 2.5 block rate for 7.5 total.
The effects of reprisal appear to be calculated
Before Block+ gear is added. Meaning Block+ gear doesn't get the *1.5 modifier when reprisal is up. So block+ gear loses about 50% effectiveness compared to what we'd previously thought. Sucks. This makes it pretty clear that Block+ gear is factored in at the end of the Block formula. This also means that Skill+ gear is a bit more attractive when trying to raise block rate. As it does benefit from reprisal.
Palisade
Palisade adds +30% block rate. With maxed JP it adds +50%. It's huge. And this bonus does benefit from reprisal. So using Max JP Palisade with reprisal up would be 75% block rate gain. That being said it's largely mitigated by the fact that you can only have it up 20% of the time.
I'm not certain how Palisade interacts with the block floor. You may have to "catch up" to the floor if negative.
Evaluating the worth of shield skill+
To compare shield skill to other options, we need to know how much block rate you get from x skill. Fortunately, we know a way to figure this out through the testing and math skills of many people.
Basically, shield skill *0.215 = block gains. This seems to be pretty accurate for the 400+ skill range.
Note that this is only for figuring out the +/- block rate from your current rate. So, if you added +40 shield skill then,
40*0.215=8.6
You'd gain 8.6% blockrate. Using this you can compare skill+ to block+ gear. Although make sure to factor in reprisal in favor of the skill+ if you do.
Block cap and floor
Block Cap. If there is one, it's not the old rumored 65%.
During early ilvl stages when SE first added shield skill+ to shields, Killedar had +215 skill. I tested block rates on the the test server and got block rates far higher than 65% with a size 3 shield.
Said test post. This is one of the better examples to date of blockrate passing 65% without the use of reprisal or palisade.
The only reason I don't flat out say there isn't a block rate cap at all is because Priwen+Reprisal doesn't cap, even when it should, mathematically speaking. It can push into the upper 95~% block rates, but I couldn't actually get it to cap. This could be a sort of soft cap to reprisal effectiveness, but that'd be very difficult to pin down.
Ochain, of course, can cap out at 100% block rate.
The Blockfloor - Where Aegis lives -.-;
Block rate floors at 5%. While the skill difference between you and the attacker can put you lower than that(call it negative calculated block rate), the observed block rate will still be 5%.
This is important because in order to get off the floor, you have to "catch up" to that 5% before you can raise block rate above it. This is much like acc/eva mechanics. Frankly, this sucks.
I think that about covers Block Rate related factors.
Block Damage Reduction
So, what determines how much damage is reduced when blocking?
There are only 3 factors for this. And two of the three are on the shield itself.
-Shield Size
-The Def stat on the shield
-the Shield Defense bonus trait
Each shield size has a set value for damage reduction. I'll go over the ones I have values for, and comment on the rest.
Sizes 1 and 2 are unknown. We just know they reduce significantly less dmg than a size 3. To the point that it's difficult to tell blocked hit apart from unblocked.
Size 4. I might have a sample for this somewhere. It's assumed to reduce more than size 3 at the cost of a lower block rate.
Base Block damage reduction,
Size 3: 50%
Size 5: 55%
Size 6: 40%
Once you have your base, then we need to account for the defense on the shield.
Half of the DEF stat on the shield is added to block damage reduction(henceforth BDR). So for say, Aegis.
40 DEF /2 = 20.
So 55% base +20 = 75% Block dmg reduction.
The final step is to account for any Shield defense bonus traits of gear.
EDIT: 2022-09-17.
Turns out SDB is a phalanx-like effect reducing dmg by literally 1 point of damage per tier. It just looked like -1% in my testing because the avg damage per hit was about 100...
Further the dmg reduction is before PDT, effectively halving the potency of the trait at 50% PDT(and it's even worse with Burtgang).
A 99 PLD has Shield Defense Bonus III.
Which is +6 to BDR
So simply add the SDB value to the current BDR
75=6=81. So 81% dmg reduction upon blocking. This is the value that any 99 PLD would have when blocking with Aegis.
If any SDB gear is used, just add the gear value to the BDR.
A few useful BDR values. and their breakdowns
EDIT:The calculations here are using the old DEF values and formulas, but the final result is still correct(un-striked number)
Ochain:
66% 60% = 40+(40/2)
+6
Aegis:
81% 75% = 55+(40/2)
+6
Priwen:
88% 80% = 50+(65/2)
+6 *
Srivatsa:
98% 75% =
55+(75/2)+6 ** See new post note.
*This would be 88.5%, but I've always floored the decimal.
I don't actually know if this is how SE calculates it, but well, you try measuring .5% dmg reduction and see if you can tell which it's using.
**would be 98.5, but see *.
New Priwen and Srivatsa Post notes(2022-09-17)
Srivatsa only has 75% BDR, despite having vastly more DEF than Aegis. It appears that it may be the case that size 5 shields just have a static BDR value rather than gaining more from DEF.
Based on its post update def and the new ilvl 119 def to BDR formula, Priwen should have had -82.5% BDR. 55+(130/4)=82.5. But this doesn't appear to be the case in practice. It only actually hits right around 80% in actual tests. I've yet to see any shield go above this value.
Shield miscellany
Other misc. shield stuffs.
Shield mastery
The
BG wiki page for this pretty much covers things... cept one note.
Old shield mastery gear, Like say, a Kaiser Schaller with a +3 shield mastery augment isn't going to give 3 extra TP like the page implies. It adds +30 TP. This is a holdover from when the TP scale was out of 300, and decimal values weren't visible. They never updated the item descriptions for these augments.
Physical WS and their additional effect vs shields
Not surprisingly, physical weaponskills can be blocked with a shield. But hey, some people don't know this stuff. And your character doesn't do a block animation when you block a weaponskill.
For multi-hit WS each hit does a block check individually.
Now for the neat part. Many WS have really obnoxious additional effects. If you block every hit of a WS, it completely prevents the additional effect. Depending on the status in question, this can be pretty damn valuable. Sadly this only applies to WS, so don't expect it to help you with nasty en-effects...
Unless those en-effects are attached to some of the rare melee type that are counted as WS. Basically anything with AoE melee hits count as WS. So do certain special melee like Gabbrath's 3 hit melee bite, iirc.
Things like
-Iron Giants(all melee. Can prevent Stun and amnesia. Super useful.)
-Gabbrath (can prevent def- and Stun. Does not block knockback)
ok, that list was shorter than I expected, but I suspect I'm forgetting some. Anyway, neat mechanic.
Shields and Ranged attacks
Ranged attacks. They're physical dmg. PDT works on them. Throughout history one of the primary uses of shields was to block projectiles.
But not in FFXI! Ranged attacks cannot be blocked with a shield in this game.
Ever notice that EES hurts no matter what shield you used? This is why. It's really, really dumb, but important to know.
That's about all that's coming to mind at the moment.
