Tinkerer's spitball is decent for tech 0. But yes, I've had a lot of dud tinkerers. Electric is nice for Sewers/Caves at least. All the self damage stuff and some of the summons just seem gimmicky, but those runs where you get a good tinkerer are very fun. Using the "get random tinkerer ability" lets you see how much trash there is.
Monk has felt pretty meh. Versatile, but I needed the "Bruise on physical hit" to really get any use out of him. Maybe just needs crazy stats.
You could do a bomber for Rad Rat, gambler for Gambit, maybe some possession cat for Dybbuk, maybe a cultist for the coven, and a mutant for lab. Not too sure beyond that.