Are the gear lists still out there somewhere?
In the OP in a spoiler tag.
The problem is the gear lists were put together around cata balancing, so they'll be off now, eg. hunters are going to need a slight nerf compared to mages, to bring their damage in line (where hunters were outright banned before, and mages could actually do damage).
Also everyone has lost a slot, due to the merging of MH/Ranged, and casters need 11 hit to be capped, where they'd only have 9 if built before MoP. Cloth wearers can now get to 0% miss against a 19 with
Flying Tiger Goggles,
Wind Rider Wand, and
Simple Pearl Ring, but the casters that can't use wands will need
Acquisition Bracers instead of the wand.
Non casters might need to get hold of the PvP weapons to match the stats the casters are getting from their wand/bracers, so that's another 70 honor needed for them.
Some people with existing 19s may find they can't get those items without dinging. On the bright side though, if you do have to reroll, at least you can do so as a pandaren or goblin now.
[edit] and if people are rerolling, can we use the chest/leg gear that we first spawn in, because some of these 19 outfits look hideous.