It is interesting with dissipation field because if you have enough damage on the board you can wipe out their quanta. I like it, and I think it is at the right cost. The unupped is pretty weak and probably wouldn't see too much play.
An idea: It might be more fun if it was swap your shield for any opponent's permanent. In that way you could possibly get rid of two enemy permanents at the cost of this card and your shield. I suppose that is pretty close to steal though.