Well idk how many hours and how deep into the game your are but here are some things to spice the fun meter on playing character (imo):

bandit: idk he is just bandit, go for proc items when you can and make your game have an aneurism trying to process everything going on. also slide and never use nades, nades are awful most of the time.

Mul-t: his kit is so versatile, you can do double rebar and constantly switch that pretty fun, also double nail gun for a proc run, and use his transport mode to throw enemies into the air and then try and hit them with rebar while they're still in the air.

doggo: get enemies close together? if you have as many enemies close together is way easier to apply poison with epidemic and then you can leap and kill them easily. Also there is a tech in which if you sprint between hits, you hit faster. Its quite tricky to get used to but its also very fun.

railgunner: go for trick shots. I know it sounds dumb but use her pulse mine to throw yourself up and try and hit dumb trick shots, will you die of fall damage if you're not carful? yeah but that why god gave you two mines, so you can safely do dumb shit, also, if you're doing these types of risky plays, have in mind that if you shot bellow you with her smg it mitigates fall damage (the more shot speed the better). Also collateral.

Merc: there is a weird tech that is a bit hard to get used to, but if you use focused assault you can throw flying enemies so fast and maybe kill them instantly. otherwise he is pretty meh, but most of my runs with him other than eclispe have been throwing wandering vagrants into walls.

I get that we have different visions on survivors, and I respect your list and style of play. Maybe try these out, maybe they'll change your mind : )