I was killing him in under 30 seconds with heroic dungeon gearI don't think that is a reasonable expectation given that most people playing WoW are probably in LFR gear with maybe some normal cache/crafted gear mixed in. You need some pretty strong DPS to not get a single massacre on 25H.
What you should really be aiming for is only a single massacre. If it happens more than once you don't have the DPS for the fight or any cata heroic stuff really.
To answer your question though, yes, there are a lot of cata 25H bosses that have mechanics that will just kill you if you don't have the DPS to avoid certain abilities. Every raid has at least 1 I can think of off the top of my head.
Now I kill him in 7 seconds or less