If you want to kill Erebus, just take rook and plant a bunch of towers. Very hard to survive against that, especially since Erebus needs to get close to do anything.
Or, stun, silence, or drain him. Many times has silence/drain caused me to either run away like a little girl, or just plain eat it.
Erebus isn't as overpowered as people think. You just got to work around his strengths. You can't attack him head on, because he'll outmaneauver you. You can't tank him, because he'll just keep draining. You need to put him in a position where getting close will hurt him more then you.