Of course we have people who don't like that Thrall is jumping in to help out the Horde or rather Baine. In order for the Horde to repair itself we need people like Thrall to help mend it. For those saying its his fault then this is another reason for why he SHOULD be here.
Well the forsaken or undead were once Legion slaves so yeah she is basically taking the Horde in a way back to its more corrupt and older roots. She reminds me of Gul'dan in some ways except she's got more backbone (heehee).