If you had been clearing NH and were decently geared for doing so, you should be good with the new raid too. Grabbing a couple pieces of nethershard gear will help with any low slots you have too. If you hadn't done them before you left, you can do the mount quests on any toon you have at 110. Each class gets a unique story. LFR this time around isn't really a good representation of the real raid, but if you are playing with friends, you can jump in normal anyway. If LFR is your only option, it still drops 885 gear. The new world bosses on the broken shore also drop 900 gear, so you can always try your luck with them.