Well... FWIW... and admittedly it’s probably not much…this is how I would trouble shoot your problem...
Start with the easy stuff... and keep it simple
First I would Use the global by-pass function on the AXE... See if you get an increase in Volume... if so, you know you need to tweak your Axe...
Second I would change the cable from the AXE to the QSC...
Third I would check the QSC with some other device... CD/MP3 player... Mic... whatever...
Hope it helps...
My system is 150W with a single 10 and theet aray... and from what you described I could completely drown you drummer out!