I think a better solution is what happened in WoW with LFR.

Just introduce the normal mode shortly after the savage version, (say, a couple of weeks after, basically a reverse of the order it came out this time). For 2 reasons;
1.) Those who really want to experience the story first, will have extra motivation to do so.
2.) Gear in the Normal Mode won't be needed for early progression in the Savage version. As any possible/reasonably-possible ilevel increase you can get, is expected to be earned for any serious raiding static.