I had Nexen on my Mk2, they were okay, but not that impressed with wet handling as the rear was really really twitchy. Falkens on Mk4 make a big difference.
Also found Nexens, tramlined on motorways, where as Falkens do not.
One thing I have found is any small amount of un-even wear causes vibration at different speeds on different road surfaces, so keeping tracking and alignment spot on all the time is a must to ensure reduced road vibration issues.
Not so use why the LS shows up issues with tyres so much, but may because it is such a smooth motor, you notice any deficiency.