I agree with your assessment that RJ may have taken Rand's agony a bit too far and in some ways he stalemated the character development for a LONG time. But, I think I know what he was going for in his portrayal of bottomless agony.

Rand is a young man who values all life as nearly sacred. His people in the Two Rivers refer to him repeatedly as a kind, caring, gentle "lad" who is helpful, slow to anger, and quick to forgive. In a place as small like as Two Rivers everyone's problems are relatively small, crime is pretty low, and people form connections that are more intimate and more meaningful than all the other societies he interacts with in his travels. This can be attributed somewhat to the fact that he is in the company of nobility most of the time now.

In a lot of ways Rand perceives all these people he is forced to interact with (and emulate) the same way the Aiel view them. They are greedy, untrustworthy, two-faced and treacherous. He is being forced to see the ugliness of humanity at the same time he is being inexorably summoned to be the savior of all. And through it all he never loses his value for human lives. His litany to the women who have died in his service compares to the actual death toll that haunts him the way a candle flame compares to a bonfire. And the real fighting hasn't even started yet.

There had to be a depth of human emotion that could actually, reasonably compare to the burden Rand has been forced to carry. Although I wish he could have developed more before the fortuitous epiphany at the end of tGS, I think Jordan did a commendable job portraying a sadness that no one currently alive could even realistically imagine.