In use and application it is generic.
1) There are MANY stealthed melee high dps units out there for harass.
2) The idea of an assasin that operates in this way is again, unoriginal.
3) My suggestion is you rethink some mechanics, try to breathe new life into the concept.
4) I have a unit in LotD, a tauren Shaman, who has an ethereal form, with a catch, the unit is invisible on the radar, and only has a faint 'distortion' effect to the visible eye. these units do not auto aquire, and will not be attacked back unless the opposing player SPECIFICALLY targets them (they are targetable, but produce no selection circle) or has a detector which nullifies this field.
A kind of new way to approach the same end would produce a much more interesting inter-tech relationship in the game, producing new ideas to counter and utilize these units, And a more fun game experience with the all new mechanics.