Druids generally have a little better health pool than most tanks. One thing I'd make sure you have ready is a boss is hitting me too hard macro on your druid. My favorite is

/use 13 (or whatever survival trinket you might have)
/cast barksin
/cast survival instincts
/cast frenzied regen (rage heal)

You can also glyph for survival instincts and frenzied regen for the insane +health and +healing that macro provides.

Also make sure your using guardian spirit or pain suppression depending on priest spec.

With all that available for your tank you can concentrate on AoE healing and tactics and brute force a lot of boss encounters.