Why is it that MPen Reds are the only real choice for mid-lane mages?
You'd think there'd be other viable choices. Flat AD? Doesn't help your burst, and you shouldn't have last-hitting issues that would necessitate flat AD. AP? Terrible value. CDR? Same problem.
Probably just a flaw of the rune system in general, but I still find it annoying that there's no realistic alternatives for mages.