What kinda gear do you need to be packing in a Dyna D group?
I think it'll depend on your group and what you are after.
I've never been super cereal about Dyna-D, but we've pulled casual 12ish man alliances together and done fine despite having some less geared than others. More serious groups may have more serious requirements, but I'm not sure how many of those still exist. It's not exactly the highest tier content anymore, it's not trivial either, but there is more flexibility esp if you are just after RP. We've made good progress through wave 3, but were more focused on RP/drops than we were killing the bosses, so keep that in mind. I've never played a critical job vs a W3 boss, so someone else should comment on that. We were also mostly drunk and fooling around when we went. We were intentionally getting charmed for instance, as part of some kind of *** up PvP system, so it wasn't really that serious any of the runs we did but we would still clear w1/w2 and chunks of w3 this way.
I've gone in on PLD, DNC, GEO, and DRK. I think the main thing is keeping yourself alive and not getting caught in squishy gear. Even the r0 Odyssey gear is helpful here. There's a lot of AoE floating around at times and you'll wanna be as self sufficient as possible, but that's true of most endgame content now. We organized parties around who had what types of gear, with more geared chars in parties with better buffers/support and those being carried more in other parties.
For PLD I main tanked a few zones IIRC, I was using Burt, full Sakpata, capped SIRD, decent FC gear, and the base JSE pieces where relevant. Nothing super special or unique and I almost think you could get away w/o Burt, but I never tried. If your DDs are using anywhere near current gear, stuff just doesn't live long, and the main risk is either over pulling or someone triggering the wrong mob. Tanking the bosses will be the main concern unless someone does something wrong. I kinda got thrown off the deep end on our first run, I joined as PLD and they threw me at it with no heads up, but it went fine despite me having 0 experience at it.
DRK same story, I had r15 Calad, full Sakpata, r20 Nyame (at the time, been a while). One of the others TPd in Sakpata but was using herc WSD gear for weaponskills, he didn't die from it. We were mowing through mobs and you could get away with less most likely. The main challenge is learning to target efficiently so you are keeping up on DPS, but we didn't really care and I venture with this content most won't these days either. There are some mobs you'll want to leave for DDs that can kill them quicker, though, if you are behind on gear.
You'll also need to consider mob types. Some of them charm, explode, or do other things you'll want to avoid. If you go with people who have experience, this would be a question to ask depending on zone, to make sure you know what to touch and what to leave for last or avoid.
Going in as 6, you'll have a higher gearing expectation. Going with 18, you have a lot more margin to not be fully geared out. The main thing I'd worry about (depending on job ofc) if you are a DD or support is staying in DT gear and knowing how to interact with the mobs/map. Just talk with whoever you are going with and see what they expect, but you can get by with a lot less than you can other content.