There is no doubt that Rand is losing his sanity. It's more difficult to detect from his own PoVs--hearkening back to Cannoli's PoV trap, the actions of an insane person appear logical from their perspective. When you read through Rand's eyes and through Rand's thoughts, ideas connect together and appear to make sense. RJ did a terrific job of this, and causes many to defend his sanity.

On the other hand, when you see him from an outside point of view, he is gibbering mad. He talks to himself, has voices in his head, falls over dizzy from nothing, and blabbers philosophical junk to nobody. From an outsider's perspective, few are crazier than Rand. We haven't seen many instances of insane male channelers--the only two I can recall are Lews Therin in TEOTW prologue, and some brief first-hand accounts during Rand's trip to Rhuidean of one of the first insane male channelers, staring curiously at people as if they were a jigsaw puzzle, and blowing them to smithereens.

Rand's personality is getting worse, undoubtedly. The ambiguity comes from the fact that we have reason to believe that the voices in his head are real--they teach Rand things that he otherwise could not know--he knows Old Tongue words, he knows about people from the AoL, knows personality traits of the Forsaken, knows Weaves like Blossom of Fire and Deathgates--knows AoL lingo. We can be certain that he has some source of information concerning the AoL and Lews Therin. But whether he's actually insane or just can't mentally handle the crazy situation of having someone inside his head--who knows? We will undoubtedly see the resolution of this peculiar case in the final volumes--whether we'll see complete separation or complete integration, or some other outcome I cannot predict--we'll just have to wait and see!