At the beginning of the game, there was another instance of "clever use of mechanics" by which conjurers could level 1-50 in a couple of days. The offenders got all the unfair experience removed when this was fixed. With this precedent in mind I don't see why SE shouldn't do the same now.

Note that I'm perfectly happy with the PLing as it is now and would like it to stay as is, but if SE now claim that this was not intended behaviour and it is an unfair way of earning experience, then they should definitely remove all the experience that was unfairly given out, along with fixing the bug that allows this in the first place.