He's not OP, just easier to play than the others.
Go ooze, right click, guy dies, talk shit, repeat.
but yeah, if you see ooze, get a wand of speed. run away.
see spit? use level 3 sedna heal, erebus mist, oak shield before a spit, or oak shield lvl 3 after spit to be clear of the dmg. It does it's damage over time, so just don't sit there and take it. Organzie your team so players that can counter spit are on the beast side of hte map.... and players that are good against ooze are on the beast side of the map etc.
All you need to counter anything in this game is team work, and items.
Overall, erebus is the biggest peice of shit ever, if u want to complain complain about him haha.
P.S. I play random proficiently, every dg is broken in their own way. but lvl 2 bat swarm = thank you for the portal flag - meet my friends the giants. thats a game breaker.... that and at level 1 with priests he can 2v1 the heath flag on cat while your other 2 demis rape their tower and cap their gold mine flag early. oh well. His "balance" is that at higher levels the returns on level gain diminishes. But games wont go to level 20 if you have a decent ereb on your team. plus.... you have oak for that late game shit. I call oak the "game timer" if you don't win by the time oak gets a decent level.... its over. haha hurray DG!