Here are my thoughts after a few dozen hours of playing the DLC.
Love the concept of the vault armors as they are rewards for completing vaults. Added bonus being able to combine them with other vault armors since the full armor bonus comes from 2 or 3 pieces only. Would like to see armor cosmetic fusion to synergize with this since having different unique armors tend to be rather of an eyesore (i.e. Wolf Vault armor + Serpentes Vault armor).
The Elder Vaults themselves, though, need some spice. Getting through them once to get the vault recipes is the only and best reward for completing them, but unfortunately recipes are just so limited that they are just repeats in other vaults. The only reason to even run through (yes, I mean RUN THROUGH because I don’t even waste time with the mobs) the Vaults is to get large quantities of Decaying Eldarium from the end chest.
Legendary weapons are also lackluster when compared to these new vault weapons as well. What made them so enticing in the Exiled Lands was that they had unique effects, better than average stats, or just some other effect that set them apart from the norm. These new vault weapons, however, bests most, if not all, the legendary weapons because 1) they are crafted items that can receive T4 buffs from artisan thralls, and 2) they have the ability to stack effects in addition to the normal weapon effect (I.e. Sunder and Bleed with the Battle Axe of the Outer Dark).
Also noticed some strange things up in the Northeastern part of the island. The enemies seem to either: have the wrong stat block or are just wrong. The ogres (or oni, whatever they are) are about as scary as crocodiles… and they’re thrall fodder for level 1-10 so that’s saying something. And the world boss brown bear? Incredibly healthy, incredibly cuddly (attacks barely amount to a tickle when hit).
Oh, and breathing potions… any point in them? There’s no hostile aquatic enemies and the Vault of the Fishmen have enough air pockets peppered around drowning only happens if intentional.
Anyways, that’s all for now. There’s always bugs and other stuff that needs fixing so hopefully next patch comes soon.