[Ranylyn]

I have a character with everything but Boxer unlocked. I went through every class. I could not find a single blue circle. I'm assuming you mean instead of the red crosshair? The Blue Square, maybe?

The Red Circle indicates it's a targeted skill. It affects characters and mobs.
The Blue Square indicates is affects a location. Creating tiles, teleports, etc.

I legitimately cannot find a blue circle.