Tyre wear is fine. Alignment has been checked and redone to help with issues. They're pretty new so very little wear. Last pair rear lasted really well even wear. Always had issues with front inside wear however.I don't mind the Yokohamas, I had them before the Maxxis and they were fine. 33psi is a little lower than I run mine (36 when not towing, 40 when towing) so you should have better grip (more rubber on the road).
I never found the Yokohamas excessively slippery, I rate their grip about on par with Maxxis and well above that of the BFGs and Continentals that I've had on the car.
So I doubt it's your tyres, unless your wheel alignment is poor. How's the wear pattern on the front tyres? Are the back tyres wearing flat across the tread like they should?