it's not just the repetition

Though that is the most easily ridiculable. It's that they use the same piece of art for things that are very different conceptually. Take this little glimmer thing for instance.

It's used for an attack spell for Mages, (Arcane Explosion i think) but if youre a hunter, it's a switch that shows which of your aspects is currently 'on' Also, for Warlock's pets subtoolbar, it shows which pet ability is currently active.

Those are two different uses of that piece of art, two completely different concepts. You should never use the same art for things so different.

While i'm at it, i don't like the use of a piece of art as a switch to show that an ability is on. not only does it make the icon different, but it covers up what is there. You can't tell what's on, you can only tell what's not on. Do you see?

A better way already exists in the game. In the hunter's pet toolbar, there's a little animated marquee border that appears when an ability is on. This is a good solution, it does its job, tells you the ability is active without occluding the ability.

Now how come the hunter's pet toolbar uses this method, while the Warlock's pet toolbar uses the occlusion method? The only thing i can think of is that they were done by two different people.

Consistency. consistency is important for an interface.