The Imp has an awful lot of counters...please play more before thinking he's overpowered...if you need suggestions I suggest Citron, Corn, Chomper, Peashooter, and Cactus.
All they did was make it harder for the Imp to get one shotted which happened to him quite a lot and make it so he's not such an easy target anymore. It's true more Imps will start to appear now because of the buff and also Rose's made him incredibly unfun to play in general. In this case it's always best to consider the fact that he has many weak points:
Citron has his Empeach if Imp gets too rowdy and plus your shield when fighting his mech makes 1v1ing a cinch.
Corn has his Husk hop which will either kill an Imp easily or greatly lower his health or throw him off guard. Also husk hop and Shuck Shot make for a great combo against the mech as well.
Chomper is strongest when fighting Imp out of Mech. Just a simple goop and bite/spray will take care of the problem right away.
Peashooter no matter which one you are, you can take out an Imp with lead shots. The Imp is mostly one giant crit box, so keeping up with him in hyper can make taking him out easy. And as for Mech, landing a bean with hyper or getting in gatling mode can also take him out in seconds.
Cactus is usually intended for those who prefer to snipe and though they nerfed Zen cactus who use to one shot him easily on her final shot; but you still only need a few chances to knock out an Imp. But again this is for more skilled players...it's all about aim to keep up with Imp.
