maybe a good ground type. they are immune 2 electric, and have good def. maybe steelix, he is immune 2 poison, toxic, and electric, and like they said, u need a good def tank. i sugg for steelix: hp steel, eq, roar (pseudohazer), double edge, or w/e u want: other possiblities are: foretress (it can rapid spin like he said, and also spike), and umbreon... i think u may want umbreon as your first, then bp sub, since it goes last and it wont break as easily as jolteon's would before it gets passed to shedinja. also consider quagsire, 2 immunities, can learn roar and haze, etc.
also maybe scizor first: sdance, and agility, bp, sub/swind. u can give shedinja the speed it desperately needs, give it attack, and possibly more w/ swind (altho no other stats will make a difference except maybe special attack if its mixed), or bp sub
for sedhinja: bp, sball, swind, protect. this way if sum1 sends out a fire pokemon or anything good vs shedinja, then u can bp ur stats w/o having to lose them.
also consider ninjask for bp speed/attack and possibly sub