Granted, I didn't like whiny, angry, unreasonable Rand at all while he was around, but I think it would defeat one of the important themes of WOT if it turned out Rand was just under Graendal's compulsion. The whole point of Rand becoming insane, unrealiable, and generally sour was to show the wrong way to deal with adversity and conflict while trying to retain your humanity.

Rand focused too much on the philosophy Morraine presented to him; "say a prayer for the dead, and move on." This just didn't work for him. He needed to grieve, and by not allowing himself to, he began to crack. And because he began to crack, he started to distance himself from the people and things he cared about so he wouldn't get hurt. Sure, Rand's inability to cope with loss lasted way too long. As a writer, RJ should have wrapped it up earlier. But the fundamental point of Rand's struggle to regain his humanity is totally destroyed if Graendal just compulsed him.