I'd say Domino with AT LEAST the Masacre synergy (+1 seconds on debuffs means infinite parries in labyrith), but the full flaming trinity makes her much more fun (Red Hulk you'll have to fight without the heavy spam though...). I'd say Sparky's synergy with Kamala and Miles is the best one for him, and Hyperion probably wouldn't have too much use in Labyrinth...You seem to have the champions to take on the easy path. Just remember to only go into the inside of the Labyrinth for Colossus.Really, you only need Domino to take on the easy path, but yeah if you're good at playing him, Sparky can be a good secondary champ to have (don't use him for Maestro though; tech champs suck for fighting the guy...).
Dominoes synergy with Massacre guarantees at least 1 second on a parry stun when limber eliminates it.