Surprise! I'm not dead!
Psionic duergar: a variant of a variant. Regular duergar were given a +1 rating, which probably is fair given how much stuff they get.
Honestly, the differences between regular and psionic duergar are minimal. The former get 1/day self-only Enlarge Person and Invisibility: the latter instead gets self-only Expansion while keeping Invisibility. The only notable difference is how the duergar's caster level is going to be somewhat higher, and how the psionic variant gets focus and psionic feats, but it doesn't matter enough to warrant a different LA.
+1 it is.