BC996TT

I have Pirelli Rossos on my 04 A8L and am experiencing really strange tire wear on just one tire.

I had the 2 rear tires changed by the dealer about a 1 1/2 years or so ago b/c of uneven wear. They did an alignment job and rotated the new tires to the front and like new tires on the front to the rear.

6 months later, i got 2 new tires b/c of a flat in one and bubble in another.

The other day, I noticed that the front tires are still in like new condition, the rear driver side..moderate worn and the passenger rear..COMPLETELY Bald!!! The car handles and rides well...with no drifting from one side to the other, so I think the alignment is ok? I havent hit any bad potholes, etc. since the last tire change, etc., so what could be the cause of this?

I have yet to go to the dealer as they will simply say I need another alignment job and 2 new tires.

So here's what Im thinking....

Change out the 1 tire and be good to go (but, will that cause more harm than good, considering the rear driver's side rear is moderately worn?).

I've thought about making the switch to P6 all seasons so that I can just drive the car all year round without changing to snows. With that said, would it be foolish to change out the 2 rears with the P6s, move them to the front and take the front (like new rossos) and move them to the back until it's time to replace.

Pick up 2 slightly used rossos (anyone selling?)

Any thoughts on what might be causing the unusual wear?

Thanks