I guess my issue is with spells that don't really need a line of effect from the caster to the target. You can see the target and presumably sound can penetrate - there's nothing stating you can't hear inside a wall of force. So, if I drop a wall of force around the target and then Banishment, would that work? After all, I just need to see the baddy. What about Phantasmal Killer? Again, I just need to see it.
The problem I have with Wall of Force, isn't that it ties up one of the party's casters. It's that if you have a few casters in the group - then you can get around the negatives of the Wall pretty easily and more or less autokill anything that cannot teleport.
I watched the party Vicious Mockery the baddy to death and there was nothing that could be done about it.