Okay so this is how I see the team so far...

Tacticians/leaders: KF, My char, Batgirl, Mason
Controllers: Druid, Djinn, ember
Tanks: My character, superboy, geb, mason
Agile&speed: KF, batgirl, Rachel, sayakea
Stealth: Batgirl, Rachel, Mason, Sayaka, 
Air combat: My character...
Great Combinations: 
Druid & geb (you know why)
Superboy & Rachel/sayaka ( They take everyone out with ranged weapons while he fights up front)
Mason & Djinn ( Mason's abilities might work well with her's)
Rachel/sayaka & Mason (again, stealth/ranged & tank mix... Though they might also get in eachother's way stealth wise)
my char & Ember (Dragon of fire&frost and a pyromancer would make very devastating things)
KF &superboy (Speedster & Tanks are fucking scary together)