In terms of class, BDK. I have been healing a long time and I still reflexively use CDs when I think my tank is suddenly about to die, if only because there have been just enough instances where I thought “Nah, they’re blood, this is fine” and before I finish that thought, they’re dead.
My favorite…? Maybe pally or monk. I don’t know that I have a favorite, I’m mostly equally ambivalent except for the DKs. No disrespect, some of the best tanks I’ve played with have been DKs, but y’all fool my FitBit into thinking I’m exercising. :]