Keiran Lee is a terrible performer and is proof that just because you've got a fat long cock doesn't mean you can fuck. I've rarely seen a scene where he gets a great performance on with his partner.
Mick Blue used to be good, he had a solid stroke game and really used to work down his partners. His recent Vixen performances are just not that good tho, the guy is not in great shape, and he doesn't get as hard as he used to. He needs to hit the gym, if you want your dick muscle to keep up with your age you need to keep the blood flowing.
Isiah Maxwell to me has never been that good of a performer, his stroke game is pretty lacking. No rhythm to his thrusts. But, he gets booked because he keeps himself in shape and he is probably visually appealing to the core audience who consumes black man/white woman porn the most, white males,, because of his long dick and low hanging balls.
If I had to name the best mainstream male performers right now, I'd say Ricky Johnson, Alberto Blanco, Jax Slayher and Christian Devil are the best workers. They know how to really dick down the female talent.