I'd like to first cite this:
http://wiki.ffxiclopedia.org/wiki/Estoqueur%27s_+2_Armor_Set
For those of you too busy to search through it, At the bottom, it implies that wearing the full set grants a bonus above expected with the previous pieces.
Elaborating, 2 pieces extends Duration of buffs casted on others under the effects of Composure by 10%, 3 gives 20%, and so on. 5/5 Expected bonus was 40%, however the bonus is 62.5%, proving, more or less, that it appears full +2 Set grants a bonus to the "Set bonus" beyond expected values.
now, With optimal gear on THF, it is possible to reach 24% Haste and full 5/5+2, (25% if you wear Rapidus, I would not), through means of the following:
*Raider's+2 Head - 6%
*Raider's+2 Body - 5%
*Raider's+2 Legs - 5%
*Twilight Belt - 7%
*Tiercal Necklace- 1%
This totals 24% Haste (About 1.4~% from true haste cap)
Now, The assumed value of Triple Damage proc on THF+2 with 2 sets was 1%, 3 2%, etc etc, up to 5/5 expected 4%, now, If its like RDM set, it means we might expect to see about a 6% Proc rate on 5/5+2, 3% more over 4/5 (Which is usually required to cap haste safely for THF).
Now i know the "Triple Damage" is not a straight mod, there is something further at work here, as with a short test on Fear (?) mobs in Abyssea-Altepa, my Average SA in my TP gear showed about average ~900~1,100 Damage (which for the test was 5/5 THF+2). Activated a "set bonus" to see a 4,300 Damage Sneak Attack, Well beyond expect "3x" Value of 3,300. Others have reported strange Damage spikes beyond the norm, so it could not be just a simple "3x" mod.
No, I know its usefulness will widely vary based on your current gear/buffs due to them having a direct impact on Triple Attack rate. I'd like for the sake of Argument to assume a 34% Triple Attack rate:
10%Base(merits)
3% Head
3% Ring
3% Dagger
15% AoA
There is also a bit to factor in current Haste (buffs/songs), Dual Wield, etc, to determine if you're getting truly that last 1% haste as well.
I'd like the opinion of fellow THFs. I have found myself in Abyssea TP'ing in 5/5 THF+2 simply for the added rate of Set-bonus rate, And it is to my liking, seeing ~600 DMG Critsx3 in succession with some luck has favored me toward it. But i often times question is validity or usefulness.
So, In conclusion, I question, Is the assumed gain of a 3% chance to 'Triple' your damage output via Triple Attack worth a sacrificing in 1% Haste value? 0.~4% if using Rapidus?
I would much appreciate any Input and discussion on the subject, as i really have no other person to ask.
(The one i did usually ask has more or less been on hiatus for a while)