The problem I found with these communes really wasn't the cost, but the balance between casting time and duration. A lot of choices in fights are kind of reactive where you need to respond quickly....and when a fight suddenly goes down, having the option to heal and cure it over giving a higher resist (which still isn't 100%) - it just didn't seem beneficial.

I'm on the boat to increase the durations but another option would be just a quicker casting time. You can't see a fight, sit outside and cast 5-6 things beforehand with high mana costs - it's usually not worth it.

Walking into something you KNOW will disease/poison you that's not during a player fight? Yeah, maybe...but that's a single supplication for a single case where a cure usually is the better option