I'll get flamed for this but here goes;
Scalloping is normal with Kenda fronts. It doesn't affect safety or handling or balance. I've got two RTs with 15k and 17k, original Kendas in the front with plenty of wear left and I don't feel compelled to spend the money to replace them.
Severe cupping is something else. That's an indication of out of balance, but you would have noticed that as a vibration in the front end.
The Kenda rear tires have a very short life. Most of us here get 9-12k miles at best on them. However, they are a very good tire and you can't go wrong having the dealer replace them with Kendas.
I have General Altimax on the rear of both my RT's. I do my own work except for the mounting of the tires on the rims and balancing them. And, I don't want to have to do that job more than I have to, so I opted for the General Altimax. Others like Kumhos, some like Yokohama, etc. There are trade-offs involved and unless you are an extreme rider and understand and can benefit from the performance characteristics of the more exotic tires, then as I say you might stay with a proven, common tire like the General or the Kumhos.
If you go with car tires, understand you may not be able to convince your dealer to mount them on your bike. That's a whole other topic, and there are plenty of threads here on the forum talking about just that.