Banette, Leavanny, Shedinja are all bad. Mismagius, Alakazam, Dusknoir are really only good to use in UU. Dragonite would be a nice contender, since it resists all 3. Bulky Scizor could also help you. Skarmory, as well.
Screw Magmortar, I'm going with Skarmory
-X-Scissor -Fly -Flash Cannon
EV's 252 Attack/252 Speed/4 Defense
btw, would anyone mind battling me when my set is done? I would like to try it out .