Sentinel's is not OP, I think the AF should be better than sentinel's. Paladin has to mix-and-match gear to different fights for sure. As it stands tanking on paladin is a lot of work, tanking on warrior isn't. So for every really good paladin there's 10 bad ones (not a fact, just observations maybe?) and for every really good war there is maybe 0.5 warrior's that are really bad (again, not fact, justobservations).
If paladin ever does get buffed, those really good ones will straight up own a whole lot of fights.