I feel your pain, some GM's are pretty caught up in their own interpretations of the rules, but he's doing the group a disservice by making you have to have line of sight on the enemies in order to cast this spell. It's not over powered if you are able to get your friends' help in directing you where to place the ally, it keeps you safe as the healer for the group, and it's a smart tactical move on your part. As a GM, I'd actually reward you for thinking outside the box like this.
As it is, I understand house-ruling, can respect it, and do it myself for some things. Perhaps your GM is doing this rule this way, in which case he probably should have a sheet of written up house-rules for the group to live by/reference and have the agreement of everyone to change an existing rule to something that he likes better.
If he thinks that the RAW of talking in combat is a full round action, he's absolutely wrong in his interpretation and I've
linked the SRD about Combat and below is the section from the SRD that explains what free actions are.
If he thinks I'm wrong, tell him to go to the Paizo forums and ask in the rules section, the developers of Pathfinder will answer questions and he'll get the same answer that I've linked below about speaking in combat.
Free Actions
Free actions don't take any time at all, though there may be limits to the number of free actions you can perform in a turn. Free actions rarely incur
attacks of opportunity. Some common free actions are described below.
Cease Concentration on Spell
You can stop concentrating on a spell as a
free action.
Drop an Item
Dropping an item in your space or into an adjacent square is a
free action.
Drop Prone
Dropping to a
prone position in your space is a
free action.
Speak
In general, speaking is a
free action that you can perform even when it isn't your turn. Speaking more than a few sentences is generally beyond the limit of a
free action.