I think you're making far too much of a largely inert feature. World of Warcraft never had a characteristic buy system, and it still manged to be great fun. I do wish they'd offered some graphical customization, but I'd rather they make the gameplay fun and compelling, especially given the relatively small scale the character's look is going to occupy.
Letting players pick characteristics isn't really customization, it's just an error-introduction system, as Diablo II clinically proved.
Well, if you're patient enough to re-build your level 90 Amazon when they nerfed Guided Arrow into the toilet, more power to you. Me, I was FURIOUS. How did the first hammerdin get built? When somebody sat down for a few hours with a calculator and figured out how epic blessed hammer could be made. Which is the REAL point behind ditching that type of customization. After playing 8 years of WoW and needing to consult the spreadsheet gurus on ElitistJerks to figure out what the most effective build is, I'm OVERJOYED that I can switch my skills on the fly whenever I want to.
Because permanent builds and intrinsic imbalance ARE a problem with game design in the real world. The platonic ideal of perfect game design might be able to reconcile them, but we don't exist in a perfect world with perfect game design. Unshackling them from having to balance every skill to a nicety saves both Blizzard and their players from tons of grief, pure and simple.
I suggest that the what makes your character yours is that YOU are the one playing it. You use the abilities you want to because you like them, not because they're the most mathematically efficient method for extracting gold from mobs. If you really feel the need to level the same character 3 or 4 times to get that level of attachment, feel free. I'll be on my level 60 Witch Doctor, throwing spiders onto Diablo's face, then laughing at him.