noticed that when burning at 8x with Nero the buffer would drop to like 7 percent for maybe half a second
That occurs twice when the burn speed shifts from 4x to 6x to 8x.
Your experince with TY is certainly not normal. I would point out the playing the discs all the way through is the best test, DVDInfo has been known to return errors where none exist, likewise for Nero verify. This is likely often due to IDE issues that interrupt the data stream. Unfortunately, short of a PI/PO scan, there's no way to really confirm burn quality, but a visual inspection of the burned surface might reveal problems, as you have seen. However, the different burn speeds used can and do create those rings too.
Best suggestion is to try a different batch of TY and see if the problem persists, if so then the burner is suspect. Are you sure that your media comes from a reliable source?