Norrathian Slayer achievement questions

I'm planning to give the new AP system an honest go in an attempt to try a completionist character. Would working on this achievement within appropriate levels be reasonably feasable, even spreading experience out between sixteen classes? There are quite a decent number of rares to knock that one out, it looks like. Prior to 51st level, fast as hell leveling experience is all-but-forced upon players on every server. Would completely outleveling the content be an issue?

If that does end up being within reason, I'd like for the character to work towards those same sort of achievements for Kunark, Velious, Luclin, etc. Am I being realistic here? Or would the character end up having to bottomfeed for almost all of this older content, regardless of how I try spreading the experience out?