I automate all the individual tracks first. Then I automate THE AUXs for overall level in the mix. Then I add compression, EQ if needed, TO THE AUX TRACKS. Unless there is something seriously wrong with the vocal tracks, most of the time they all need just a little hi end and a little filtering. So instead of having 25 Oxford Eq's open..I'll have 2. If there's something wrong with one particular vocal, I'll eq that separately.
Hope this is helpful.
I feel putting your compression in the group channel is not the right thing to do. Instead of "seeing" a vocal track and working on it's dynamics the compressor sees a sum of signals and compresses accordingly, which means that when one track is loud at one moment, all the other tracks are compressed as well that moment. Even if they dont need it. To me that's against the purpose: You want louder parts of one track compressed, so that the other tracks that arent as loud dont get lost. Or am I wrong here?