Better question to your suggestion. What advantages would it give the shaman for being able to place them off the GCD? Would it make any difference? Would it make people start macro'ing certain totems to abilities.
Not saying it's a bad idea, but for it to be a good suggestion you have to be able to analyze it from all directions and say why you believe it would be a good suggestion. At the very moment (just quick thought and haven't really thought about it) I don't see any reason for it to be off the GCD other than just to say that it was "buff" to shamans since they can't place them while silenced.
Would be really nice for ele/enh no longer having stormlash and FET on GCD for opening burst spirit link would be easier to use but I dont think it would make a significant difference to the overall survivability of the class.
I'd like none killable totems. Give us back call of the elements and make the totems stack on top of each other instead of beside each other. You would not believe the number of failed capacitor totems I have placed because of the placement of totems.