question about instances

[SPenguin]

I feel dumb. I am leveling an alliance warlock (level 39) and it feels like bosses are harder to kill. I went into deadmines to farm cloth and couldn't get past the second boss. Is there a change in MoP or am I missing something?

[Nobuemon]

For deadmines specifically there is an issue in the heroic version on the final boss, the others should be more or less fine