I was thinking how crappy dying to "circles" you can't see is. They can end up partially/entirely clipping through the ground, or up in the air from players jumping, or from all the player made circles. I was thinking how much easier they'd be to see if they were somehow 3D but kind of dismissed the thought since SSG probably didn't want to figure out how to add that to the engine, but then I realized, we already have something like that: Wall of Blades.
So, my suggestion is to change the game's circles into a 3D effect, similar to wall of blades, but a different sprite (instead of blades, like some kind of rune ribbons like other spells have). Easier to see, and much more resistant to clipping or other visual problems.
Also, note, the height doesn't have to be the same, they could be shorter. This would probably be in addition to the existing effect, but maybe not? I don't know how DDO's engine works.