A lot of these missions require an annoying amount of micro management for melee characters.
On certain maps, melee characters completely fail to route to some of the positions where ranged enemies spawn in, even though there is nothing blocking them, so they just stand there taking hits until you manually pick 'em up and move them a few pixels over each time one spawns. On some of the maps when things get crowded, that can be hard to notice that your guy isn't swinging at an enemy a few pixels away, as they slowly spawn more and more there.
Yeah, I know, melee's are pretty useless in general, should only have one. Just pulled orc girl and the soldier girl, and was trying to level 'em up some.