On my Nokia Lumia 822, I have experienced no framerate drops or crashes. Very rare audio stutters, but that only happened when an achievement popped or it was loading the end game results page. I've only finished section A, so I'll have to see if anything changes as I continue. It seems like your issue is not that uncommon according to multiple reviews sadly. But, I'm pretty sure Microsoft will be doing a lot of tweaking with their already announced patches.
Hope you can get it running in tip-top shape soon.