This is the one peeve I have about your post. Bosses were never meant to gain EXP. Yeah, you gain a lot of EXP when you do it and there's a tremendous sense of accomplishment and satisfaction after that, but it isn't as if you can go back and beat bosses again. Gaining extra EXP (more than the game requires) means going back and fighting extra tedious battles. The game is programmed for the characters to be at certain levels at certain times, so you won't be at a loss for not gaining EXP when you beat a boss.

But I can see the validity if the complaint is that you get nothing to immediately show for your hard work.

I understand your point completely. However, when you use tons of potions and other items to battle against a boss, don't you want something in return? If I can get 500 EXP by beating some weak monster without sacrificing my items, then I rather beat 10 of them than fighting a boss. While I agree that there's no need to give players tons of EXP for defeating a boss, at least some special items or weapons would be nice.