I played a melee build through floor 15 and was doing okay toe to toe with Dredmor (until he knocked me away and burned himself to death before I could re-engage) and did not feel useless at all. Probably the biggest difference in my build is berserker rage, which is absolutely huge now. Not only do you get 4-6+ extra damage and extra armor once you get going, it lets you pop out your own boosted criticals when you need to make attacks count (critical Thibault Trompements are also actually pretty decent at softening enemies up once you get really high melee power.) You can get enough health that enemy crits are not immediately threatening, but enemies with high crit+counter are really deadly if you can't break through their counters with your own crits. I would say every melee build really, really needs to either take berserker rage or go dual axe + assassination to get their base crit score as high as possible.