dtgreene: What I'm saying is that mandatory "grinding" (again, I don't like the term) is a perfectly valid game design decision. A game requiring this to progress does not automatically make it a bad game.
Mori_Yuki: Would it help to call it: Repetitive tasks? Because that's what it ultimately is. It can work and in certain cases, while in others it just shows lack of imagination. Putting in stretches you must kill red slime, green slime, blue slime and purple, just to get from level 1 to 15 - mind you, that's hardly ever the case with clever character builds, even in jRPG, that's where it ends being fun or necessary.
Again, we aren't to far off from each other, the only thing i disagree with is implementing repetitive tasks, when there is no need for it. In most cases i played that's a choice not a design-god-given necessity. The main thing here is that this isn't about jRPG but games like the one OP mentioned. I think we can agree that in most those cases there are alternatives to repeatedly killing, collecting stuff etc. That's Diablo, that's MMOG, not RPG.
What I'm saying is that it's a valid decision for an RPG to be built around performing repetitive tasks just to get numbers to go up. For an extreme case of this, see Disgaea's post game, where levels can go into the quadruple digits and stats into the millions (and I hear the numbers get even bigger later in the series).
Interestingly enough, I've also seen this sort of thing appearing in idle/incremental games, like Cookie Clicker (being the most famous one, but certainly not the only one; other good games of the genre include Candy Box 2 and Universal Paperclips). Sometimes, like in Cookie Clicker, the whole point of the game is to increase a number as fast as possible, and the mechanics are complex enough to make it interesting. (Also worth noting that you do get AFK growth in these sort of games; Candy Box 1 and 2, for example, give you one candy per second right from the start.)
Edit> Why the low rating? What's wrong with me stating that sometuimes I want games where I just wantder around in circles, killing enemies, and watch numbers increase?