Reasons for Alt-Tab'ing differ situation to situation. Mainly do it while waiting for a mission to roll or while on a long flight. I actually don't see AH as resource-hungry as other games I play.
Texture loading aside, my system seems to handle my Alt-Tab'ing well enough. I can handle the texture load when coming back in to the game, but it's the first load of the arena that kills me. I'm not unlike you, though. I've come to realize that I will probably always have this problem so I use the opportunity to check out the squad roster, see who is where, grab a drink, and get my flight area ready.
But still, this texture problem is annoying and hopefully it can be corrected in the future.