I don't think bite is OP, because a basic favor item is enough to defeat erebus, provided he doesn't get to equip a favor item himself.
An example game from yesterday: I chose erebus. My opponent chose oak. The game started, I bought the two cheapest armors available, then set out to the nearest flag. When I got there, in comes oak. I bit him, then ran left towards some other flags. I should have been able to outrun him. But I couldn't - oak ran me down, and started swatting at me as I was running. At that point I tried to get back to my towers. I'd quickly turn and bite him, then turn and run while recharging the bite, then quickly turn and bite him again, then turn and run while recharging the bite. I never made it back to my towers - he killed me.
I asked him "Why are you faster than me with oak? Are you cheating?" He said "No - a favor item, 25% speed increase." I said "Oh okay, well I can't equip favor items so... cya."
The whole point of that story is, if bite were so OP, I would have won that engagement, don't you think? If you don't believe this story, play it out yourself. Take erebus, give a competent friend oak + whatever favor item gives the 25% speed increase, meet him on the field of battle, and see if you can bite and run away.
By the way, I'd say I'm a decent player because I win 9 out of 10 games I play. So decent erebus minus favor item against decent oak with favor item = win for oak in the first or initial engagement.