People take low stage volume WAY WAY WAY to far. Low stage volume is just as easily overdone as anything else. The guitars and bass at least need to be loud enough to be heard by the band over the drummer behind his little plastic wall. Turn the stage down too much and you sound terrible, there's no punch and you get feedback and bleed-through like crazy. You might as well have everyone go direct through an original POD if you're doing that.
Churches are usually the worst offenders of too low stage volume, band leaders spend too much time reading "the new in thing magazine" and not enough time learning how something sounds good.
In my experience the plexiglass screen is a BIG help - the drummer still may need to play with hotrods, but you can mic the kit more easily and I find it cuts the overall necessary volume down quite a bit, mainly because it tames those cymbals sizzling right in the other musicians ears and keeping them from hearing their parts. There's less need to turn up amps or monitors to compensate. It also helps the snare pick up fewer sympathetic vibrations. Ive always coupled the plexiglass screen with a drum riser to decouple the drums from the rest of the stage a bit, and raise the directionality of the sizzling high end over most peoples heads. Doesn't have to be too high up, some 2x4s with plywood nailed over and carpeting stapled down does the trick.