Oh, yeah, that's a terrible idea.
I don't agree that Dwarf is ok just being an off tank.
Kheldians must be able to tank, actually tank, on teams. If its restricted to Dwarf, allowed in Human or even Nova or not. In AT LEAST Dwarf form Kheldians must be able to actually tank, with an aura. I would prefer giving them a human form punchvoke option in addition. I like the idea of Nova too, but I can see that's more iffy.