Full skill with Mistilteinn/Nms+1 is +40 MND and 344 enfeebling skill
Full skill with Mistilteinn/Astral Aspis is +41 INT and 344 enfeebling skill
For those numbers, I'd assume you're using AF body. Losing errant body for AF costs you 10 mnd(11 with mahatma) and gives you 15 skill. Correct me if I'm wrong, but staves give +10% magic acc on NQ and 15% on HQ. This would put a HQ staff equivalent to at least 45 skill for a loss of 11 MND on slow/paralyze >_> I always put staff on first before any skill pieces, though I only have mythic+1/nms+1 and no mistilteinn.