So, I went feral after my favorite resto spec became almost unusable in PvP due to survivability, throughput and utility issues. My feral gear isn't the best, but it's quite good: a full ilevel 378 PvP set, 2 pieces of ilevel 390 set, a 378 PvE weapon and a good PvE trinket. I'm probably not the best feral druid in the world, but have some experience and more or less know what to do.
Usually I don't have a problem killing other players, sometimes I even get lucky and manage to kill decent frost mages, I can kill a resto druid (lol, who can't?) and a disc priest, although the latter takes a while and requires good timing. It's holy paladins and resto shamans that I can't kill: equally or even worse geared paladins or shamans seem to be able to easily outheal whatever damage I do, despite I charge/interrupt on CD, and don't seem to run out of mana. Yesterday I caught a lonely holy paladin and went all out on him for ~5 minutes, but he just stood still and /lol at me: his health would never go below 70% and his mana was always full. Eventually his teammates came and killed me.
This is pretty much what I'm having with both holy paladins and resto shamans: they take minuscule damage and never run out of mana, despite I stun and/or interrupt them every other time they attempt to cast a big heal. So, my question is: how do you kill them as feral?