It certainly skews balance. At least with point buy you can balance around a certain expectation, with rolled stats you just sort of have to give up and balance towards an average.
Adjusting difficulty levels does the same thing. The easiest setting is quite similar to having +4 to every attribute (perhaps not quite that good because it doesn't add to damage, AFAIK). If you want an "easy" experience on Tactician difficulty, maybe all 18's would do the trick. Accounting for random rolling is as easy as accounting for difficulty levels.
