Well, since different characters don't really add to the chess game it doesn't really matter but I use:
Shujinko as Leader
Noob-Smoke as Champ
Sub-Zero as Shifter (I'm good with him but not so good for grunt/champ and just incase he fights another shifter I'm good to go)
Jade for Sorceress (she looks cool as one, and I'm decent fighting with her)
Scorpion as Grunt, (he's my best fighter)

Noob-Smoke Leader
Sub-Zero Champion
Zombie Liu Kang Sorceror
Kenshi Shifter
Scorpion Grunt

Sindel - grunt
Mileena - champ
Ermac - sorcerer
Kenshi - leader
Jade - shifter

I use:
-Rayden=leader
-Sub-zero=champion
-Scorpion=sorcerer
-Ermac=shifter
-Liu kang=grunt

Leader: Ermac
Champion: Mileena
Sorcerer: Baraka
Shifter: Kabal
Grunt: Kira
will probably be trading Ermac out.
All I really need is Kira though, not that often anyone gets to my other people with her kicking all the ass.