DK is not exactly a base killer (of course with the right pet and patience she could..) I don't find her handy in Insane Dungeons (7+) or HBM.
So depending on the mode you play there are definitely better heroes then DK. So, are you looking at each individual mode? or overall usefulness of heroes?
well like all others said it depends on what game mode, she is usless in insane 7+ and she can either be built crit striker or a healing tank, mostly those two like Stealth and Survival and healing ritual or BF and UP/SL with Fictory Lunge, and some go with vigorous fury and UP/BF but hey, there is many ways she can go so it depends on what your going for as Shampz mentioned.