Yeah, Zev and Isabela used to die so fast even on the lower difficulties, while for 2h, I loathed using Fenris and Carver in DA2 for having the uncanny ability to never hit the enemy and instead decide to make it their personal mission in life to one-shot Hawke. Carver I can understand doing it on purpose, but dammit Fenris, I thought we were pals!
XD Fenris was godly for me. But yeah Zev and Isabela were too squishy. The annoying thing is rogues are ridiculous when they're played properly so it was clearly an AI issue.
Then I got the whole party one shotted by Fenris in the fade. I was stunned then I burst out laughing. But yeah I liked 2hders in the other games (and despised archery). Now my opinion has been swapped by DAI. *weeps* (not saying archery was ever bad. But I didn't like playing it).
I've only played DAO twice and used Morrigan/Alistair (shield)/Zevran (bow) as my party both times, so I don't really have an opinion on the other AIs in that game, but I totally agree that 2H got totally screwed over from DA2. I never had any trouble with Carver or Fenris. And I tended to take Isabela with me everywhere just because I like her so much, but I agree she was probably the worst companion from a combat stand point due to her AI. It helped when I invested a lot into her Subterfuge tree, but she was still never as efficient as Varric or Sebastian (although I never used him again after the first time I played after getting his DLC, freaking hate that guy).
Yeah my issue with DAO was the rogues didn't constantly use backstab without me using an AI mod. 2hder when I used it on Sten was functional (it wasn't anything astounding but it worked well enough. Indomitable really helped). In DA2 Fenris was my tank and it worked fine too. And in DA2 it seemed like a stiff breeze would knock Isabela down. (at first I thought DWR sucked period then I rolled a dual wield Hawke and was pretty much carrying the whole party. Not sure why Isabela's AI was so terrible.) Aw poor Seb. He wasn't that bad.