Yes the invasion of Quel'thalas was my favorite three levels of the ROC undead campaign, and yes even though sylvanas got 'owned' she does re-appear in the TFT undead campaign, where I found the mission where you use her to be fun. Kel'thuzad was quite a fun hero, unfortunatly, you use him very little, in ROC you finally get him in Blackrock and Roll again!, but to find you later if to protect him, and as for TFT, you use him 4 the first few levels then you leave him in Loderon. Yet I find each experience with each hero enjoyable.