From my experience so far, DB wasn't really an issue for AB as I usually stay inside pneuma and not in the front line / precast area. Regardless, I think you are still pretty lit from DB with 100mdef, especially from Tao users. I was wearing unfrozen and still getting one shotted when a whole guild spam stuffs into me. Hell half the time I don't even know what hit mein my penuma and I am back to spawn point with all the lag spikes going on.
Since you're mostly die to most stuff in 1-2 shots, I don't think taking 25% more damage to water/fire really matter as the result is the same (1-2 shot dead). Stone cursed and frozen will probably affect you more in a penuma as you can't cast lauda to help your team out. Contrary to everybody was saying, I kind of think that undead may actually be a good and effective alternative to 100mdef in WoE renewal, except maybe when entering pre cast area I just swap out unfrozen.