For those of you who have played it, I'll be appearing on my friend's DiA campaign for roughly 2 sessions at around level 9-10 and I want to make a character that'll help the party or at least make some encounters interesting

They have a champion fighter, 2 rogues (Thief and Phantom), a Bard, a cleric and a wizard already.

If all goes well, I'll be appearing when they reach the citadel, after hangman's hill. I'm considering making a frontline since they seem to be lacking a bit in that aspect, so I was considering either a paladin (watchers or redemption) or a zealot barbarian with medium armor played like a paladin who wants to help save Zariel (from what my friend tells me, the party is set on killing her but both he and I know how much more fun it'll be if she manages to live and rid herself of her corruption somehow, not sure how that'll work yet but I think my friend knows and just isn't telling me XD)

What do you guys think will benefit the party more and make encounters there at that point more interesting? A paladin or a barbarian to tank? Cause combat encounter wise, their fighter gets the brunt of everything 😂