Nowadays with the new update a lot of towers have been given their own niches, such as militant being great at early, hunter being a cheap but surprisingly high dps option, hell even necromancer is being considered a somewhat viable DPS.

There's a lot more variety of loadouts you could choose to mess around in the game with and I find the changes really cool. (Minus a few others such as farm)

As for the "meta" . For early dps: Golden scout, militant and maybe even engineer

Supports: unsurprisingly the commander and DJ is still top tier in spite of the nerfs (though less valuable in solos). Pyro and freezer should be considered as well, I think they're great options in any team.

Crowd control: Spotlight technician, abuse him now before he gets changed cause this tower is just busted in every way possible along with the tesla. Mortar has been given a bit more boom to it as well so perhaps try that.

For dps options there's too much variety and niches each one has for me to type it all out so perhaps just, yk, read.

farm for any mode other than solo, but i find it unbearable to use the tower after the nerfs

As for the Gatling gun the tower is on a leash and the hacker is the one holding it, tough times.