We’re stuck in this trap sometimes where players want glyphs and talents to be meaningful but optional. That’s a pretty narrow design space.

If we make a talent that affects Shield Wall, then it feels mandatory. If we make no talent that affects Shield Wall, then it feels like the talents aren’t affecting things you actually care about and can become this potentially marginalized aspect of the game.

The argument seems to be that if you didn’t have to get Improved Disciplines, that you could get some other potentially juicy talent. True. The same would be true if you didn’t have to get Shockwave or if paladins didn’t have to get Ardent Defender. You need Improved Disciplines, but they need Vindication. My point is that classes are balanced as part of their entire package. You aren’t balanced at the core level with talents and glyphs thrown on as gravy on top of that.

Now we are making an attempt with Cataclysm to give players more options in how they talent. But still if you imagine a talent tree in which every single talent is optional, it’s also hard to imagine how every single talent is interesting or powerful enough. (Source)