Just did the quest Qalian's Last Smile and Tharaêl seems to be a wimp who goes down in one or two hits from the bandits in the Tar Pit.

I've noticed that my Chainlightning spell jumps to the companion too when they're in the fray. Two or three chainlightning bolts aimed at an enemy and Jespar tends to be down on one knee as well. Doesn't seem like he can take that much damage. But he's the only companion I've been travelling with on...