Well, since Masquerain is a bug type, i don't think substitute would last long because of low defense but the Sp.def will almost balance things out . His/Her high Sp.def is an upside since most of His/Her weaknesses are probally gonna be special moves (like fire, ice, electric etc.) so, as long as you are not against something with a rock type move (since most are physical) and can set up that sub for a while, This wouldn't be a bad passer.
