I am talking to Swen about this topic. My thoughts: I think too many skills do too much. For instance, most skills deal nice damage AND set a status. This makes it so that the player never really thinks: "What am I going to do? Am I going to use this skill OR am I going to do a regular attack?" This indeed causes skill spamming. In my opinion, skills should be used in a certain context, and it should be somewhat of a hard choice for the player, and should be context-sensitive.
For instance, if a skill has a chance to knockdown, its damage output should not be as high (or higher) than the regular attack. The player will then wonder "should I hit this guy, or should I try to knock him down".
Another example: the Rush attack should only make sense if a lot of enemies are lined up so you get the maximum out of that skill. Right now, you can use Rush almost anytime, anywhere.
Another example: the Bleeding attacks of fighters/rangers/rogues should not deal as much damage as a regular attack, because it inflicts a DoT attack. You should have to choose between either DoT, OR a regular attack.
So in short, I don't think we're there yet with skill balancing. I would like to see the choice between "attack" and "use skill" become a real choice, a more tactical/strategical choice, a 50/50 choice, and not a no-brainer like it is now.
For mages, this may be a bit different, but it is again so that most mage skills do too much at the same time. E.g. they AND do damage, AND set a status OR do crowd control. E.g. if you teleport a guy, it does okay damage AND you've moved him out of the way. If you moved the enemy, that's a good thing right, why should it still take away half his damage? This means that you're going to use the teleport skill on people not to get them out of the way, but to do damage. This should, imo, not be the case.
Also, yes, the AI doesn't use skills intelligently yet, or appropriately. We are aware of that, and working on it.