I never took my pally to AV really, cos I run 1 PC and I'd rather run a bit smoother with 4 than a little slower with 5. However I've had various people mention some of the benefits to bringing him along:

1) As already stated, he can take more of a beating and tends to get focussed cos he's the lead
2) If you can sort out a nice Blessing of Protection macro he can make the difference between life and death for your followers
3) A well timed Hammer of Justice lets you easily finish off a pesky rogue or priest who's about to fear the group (better for non shammy groups than shammies, but still nice).
4) AV is 80% PvE these days, so you've got a pocket tank if everyone else is pissing about, just rush in and take down the bosses yourself (maybe moreso when you are L80 ofc).
5) The buffs are a bit of a bonus, and as you already mentioned, he is able to res (always recommended rather than ghost juggling with alive and dead team members unless you are really close to the GY).
6) Crusader Aura - Really helps to get the jump on the opposition esp. in AV, where time is often of the essence.