This is why I hate the "cut and paste/reply to one paragraph at a time" method - I prefer refuting points to be made per topic. Aviendha and Mat are relevant to the discussion because they illustrate the indirect effects of tampering with the Pattern. In this case, Rand balefired Rahvin, and caused a number of deaths to reverse, but we have no way of calculating the unintended consequences (ripples, if you will) that occurred along the Pattern because of it. This is exemplified by the fact that even though their deaths were reversed, they and others still had vague recollections of their deaths.

Thus it doesn't matter if you "only removed/burned away 3 or 4 seconds of space/time" - there are unintended consequences beyond the direct action.