Indeed. I don't want to twist the game mechanics. The long time needed to get to the highest tier is good. What I find frustrating is doing over and over again the same maps. I don't want devs to give us 3-4 campaigns either.
It would be fun IMHO to have specific survival maps (5 heroes against hordes of enemies) that grants you XP, that don't drop any pinks or valuable item. That way if you don't want to gain any experience, just disable XP gain or else "Welcome to a New world".

P.S.

Actually a glimpse of survival map are shown in the cycorp labs campaigns in SL where our heroes are litterally swarmed by the vular in multiple occasions.