Pick Skycat, if you didn't, restart on another server.
Use LaCross (You can get him in the Fairyland Shop)
Use Grout (You can get him in the league shop) He will make it impossible to lose at higher levels
Use all your genes to get Jack and Yu Gone Lose (They are the only S class heroes that matter anymore)
Congratulations, You've got a top 5 man team!
Now build all armour, M.Attack, resistance, and a small amount of HP. Physical attacks have a high rate of missing, so they aren't worth using!
If at any point you can't switch to this formula, you might as well quit. These exact same heroes have been dominating the Arena and PVP scene for months and nobody has done anything to fix it and probably never will.