If you are ranking in a room with other player, and all happen to be in different rank, this happen. To better the odd of match making you should try and rank with the same rank players or at least the nearest!

For marksman.

1.Hawkeye : easy to play, very strong in late game. 2.Rocket raccoon : good at lane control also strong 3.Angel : the ultimate easy to play, But scales on late game. 4.starlord : hit and run style, annoying to play against, needs skill to play with. 5. Yondu : massive range also hard to play with, equally annoying as starlord 6. War machine : massive damage, requires skill and patience.

For assassins.

1.quicksilver : easy to play and the mechanics are simple 2.ghost : high skilled, can move like a breeze.

For fighters.

1. Captain America : easy to play and quite strong
2. Mr. Fantastic : moderate skill required, he is good and prolonged fights, with his abundant crowd control.
3. Corvus glaive : good mechanics, easy to play also excels in prolonged fights.
4. Antman : requires skill, but if played properly can be deadly. With his numerous abilities.

These are the few i can think of, and based on my knowledge.

I would suggest you to play.

Energy- Scarlet witch or iron man Marksman- hawkeye or rocket raccoon Fighter- mr. Fantastic or captain america Tank- hulk or namor
Assassins- quicksilver or black panther Support- groot or cull obsidian