I like the idea of a healer with persistent ground aoes, though the numbers may need some tweaking. It's possible I missed something in the description, but with AST stance it seems like you could just drop two probes behind the boss to form a horizontal line and have dps stack on it for buffs. Then drop a probe directly north or south of a probe for a free critlo before any raid buster goes out. The detonate would reset the probe CD and the party could just stack on that probe until another line can be created and the strategy just repeats. Also, are the probes similar to turrets in that they can be healed? Because being able to heal them would be extremely strong.

Those are just the numbers though. The mechanics and class theme are both pretty interesting.