Yes gizmo can res units.
As you said using frozen orb, it is good for blocking enemy archers but only ones with low initiative and cyclopes are really few in battles during whole game, and almost all other archer units have much higher initiative and harder to block more so if other flyers or fast units keep them protected.
For healing dragons dancing axes work but not on : plants, undead, mechanical units (cyclops and droids from crossworlds).
Glad to be of help, have fun and until they release KB-WotN
