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?
Zephrica and bloody Mary (and sasquach if the dove does not have the ability to regen) those are the only heroes I can think of that can 1V1 as dove if they both have best talent/insignia/traits. Not saying these are only ones just only that I know can beat it in sure if you out these with other people's response you will reach you 7 heroes to beat dove goal
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.
CC name: XgodAlive
I use to be f2p for two years, but now a proud p2w