Oh, man. I hadn't even considered casters as endless artillery. Unless AoEs were extremely rare, armies wouldn't even exist. From a world building stand point this would be huge. I imagine there would be a lot of skirmishes and small group raids. Conflicts would be more personal. Of course, easy...
I keep getting stuck on healing. Any heal spell becomes infinite healing between fights. I've thought of 2 possible fixes.
The first was mentioned early in the thread, 4e style healing surges that are triggered by the spell, but only if you have uses left.
The second, I find more elegant...
With 7 players, I'd lean towards something heavy on social interaction, and light on combat and exploration. Social situations can involve more players at once, which limits down time for everyone.
Maybe the PCs are part of a trade caravan. Some could be travelers or pilgrims that were adopted...