Using the right heroes in your team can give you a small team bonus, here are the teams discovered at present

Agents of S.H.I.E.L.D. +15% Max Health Nick Fury, Mr. Fantastic, Iron Man, Daredevil, Ms. Marvel, Wolverine, Captain America
Agile Warriors +2 to Striking, Body, Focus and Teamwork Black Panther, Carnage, Daredevil, Deadpool, Iron Fist, Spider-Man
Authority Issues +35% Fusion Gain Wolverine, Gambit, Magneto, Juggernaut
Best Friends? +15% Max Stamina Cable, Deadpool, Spider-Man, Venom
Bruisers +5 Striking Juggernaut, Hulk, Thing, Luke Cage, Thor, Ms Marvel, Venom
Classic Avengers +15% Max Stamina Black Panther, Captain America, Hulk, Iron Man, Thor
Defenders +2 to Striking, Body, Focus and Teamwork Hulk, Ice Man, Luke Cage, Ms. Marvel, Wolverine
Double Date +35% Fusion Gain Black Panther, Invisible Woman, Mr. Fantastic, Storm
Fantastic Four +35% Fusion Gain Mr. Fantastic, Human Torch, Thing, Invisible Woman
Femmes Fatales +5% Damage Invisible Woman, Jean Grey, Ms. Marvel, Psylocke, Songbird, Storm
Former Horsemen +10% to All Resistances Wolverine, Hulk, Gambit, Iceman
Heroes for Hire +10% to All Resistances Deadpool, Hulk, Luke Cage, Iron Fist
Martial Artists +5 Striking Captain America, Daredevil, Deadpool, Iron Fist, Psylocke, Wolverine
Marvel Knights +5% Chance for Critical Hits Black Panther, Daredevil, Hulk, Spider-Man, Wolverine
Master Minds +15% Max Health Iron Man, Magneto, Mr. Fantastic, Nick Fury, Spider-Man
Masters of Energy +15% Max Health Cable, Gambit, Jean Grey, Iron Fist, Ms. Marvel, Nick Fury, Penance
Maximum Carnage 5% of damage inflicted as health gain Captain America, Carnage, Iron Fist, Spider-Man, Venom
Natural Forces 5% of damage inflicted as health gain Human Torch, Iceman, Jean Grey, Storm, Thor
Natural Leaders +5% Experience Black Panther, Cable, Captain America, Jean Grey, Mr. Fantastic, Ms. Marvel, Storm, Magneto, Songbird
New Avengers +10% to All Resistances Ms. Marvel, Spider-Man, Wolverine, Iron Man, Luke Cage, Iron Fist
Pro-Reg Heroes +15% Max Health Iron Man, Mr. Fantastic, Deadpool, Songbird, Ms Marvel, Spider-Man
Secret Avengers +3 Teamwork Cable, Captain America, Human Torch, Invisible Woman, Iron Fist, Luke Cage, Nick Fury, Spider-Man, Storm
Secret Warriors +5% Damage Wolverine, Spider-Man, Captain America, Daredevil, Luke Cage
Shut Up Already! +15% Max Health Spider Man, Iceman, Deadpool, Human Torch, Thing
Think Tank +15% Max Health Mr. Fantastic, Iron Man, Green Goblin, Spider-man, Hulk
Thunderbolts +5% Damage Green Goblin, Songbird, Venom, Penance
Unrepentant Killers 5% of damage inflicted as health gain Carnage, Green Goblin, Magneto, Venom
Weapons Specialists +5% Chance for Critical Hits Black Panther, Cable, Captain America, Daredevil, Deadpool, Gambit, Green Goblin, Thor
X-Men +15% Max Stamina Cable, Gambit, Iceman, Jean Grey, Juggernaut, Magneto, Storm, Wolverine, Psylocke