I had the OE Trialwings on my 650XT and you are right there was not much impact on the handling or feel when they squared off, but to be honest that's because they were average at best (and awful in the rain) to start with. I find the mutants to be great in the dry and truly exceptional in the wet, and yes you can feel it when they square off but that's because they are so good to start with (certainly compared to the OE tyres).
To be honest, other than trials tyres I have never really got much more than 5 to 6k miles out of a rear on anybike. I would rather have grip than extended longevity, but I only do 4-5k a year so that might be why