I too am running sound for my band from behind the kit with a QSC Touchmix. We've pretty much got most of the clubs we play dialed in but there is still a need for someone to adjust levels for lead vox and backing vox, etc. So whenever possible we'll have a tech with an iPad adjusting levels appropriately but it's always better when this person knows the art of FOH sound and it's really nice when the club has a good PA and FOH/Monitor engineers but those are few and far between.
I do understand your point about importance of sound engineers not being as high as the players especially the singers so I'll admit to overselling my opinion therebut I still think a good sound person is worth the cost, IME.
It's also harder for a drummer to play and run sound than it is for a bassist, guitarist, or singer to do it, IME/IMO...

