An interesting discussion. My thoughts:
People generally do better if they are satisfied with their employment. Forcing all the banecasters to be banehealers probably won’t end well particularly given their inherent powers and likely wealthy and powerful families.
I can see some major logistical advantages of banecasting over artillery. And see some major throughput advantages of artillery over banecasting. I’m pretty sure there is some tactical harmony to be had there. How about artillery delivered bane-patterns???
Banehealing is a huge advantage that there is no modern correlation for. I once ask my father (a surgeon) if he had a choice between the magical healing healing of a wizard without modern medical knowledge and the best surgeon with all the modern tools which he would rather have he said, “are you kidding me?! Wizard! 100% of the time.”