Sadly, there's not much you can do with someone with lots of reverb, or who sounds like they're in a drain - except make them "on phone".
A couple of other things you can try:
highpass everyone. This will also pull out some of the buzz. Do it very lightly, or they will all sound like they're on the phone.
For reverbed voices - a very light lowpass filter seems to take a teensy bit of the edge off of reverb. Not much, but every little bit helps.
Try and move the characters left and right of center in a logical way... for instance, group all people with decent sound in the middle, all hollow voices on one side, all reverbs on the other. Or maybe make them sound further away.
There's a reason i love to use a lot of background noise.
--Julie Hoverson 19 Nocturne Boulevard
...and the Deadeye Kid
......and Fatal Girl
.........and Tone Didactic
............and Bingo the Birthday Clown