Yeah, that's also true as well... when I first saw Saix, I knew he was just another loyal puppet to Xemnas (who I really don't care for), but because of the boss fight with him and the new info on 358/2 Days, he's been in a new light for me and he's really not even the lap dog everyone expected him to be.
If you ask me, I think Axel should have stuck with Saix from the bginning. Not saying I blame either Axel or Roxas for what happened, but if he stuck with him and their plan, it probably would have failed anyway, but at least they would still be friends and they wouldn't be going at each other's throats. But also, in the past game, you never did see Saix lay one hand on Axel, despite his comments. This shows that maybe Saix still had a little bit of... let's say... "brotherly love" for Axel. I can also say that Saix can be seen as a big brother to Axel as well because of how much he's a guide for him in a sort of way, because of how much he bosses Axel around and shows him paths.
That "brotherly love" thing was kinda meant as a joke, but even so, their bond with each other is somewhat sad but so... beautiful. I would blame Xemnas because he had already known of their betrayal but kept quiet about it and watched until it fell apart.