Players are intended to be Elite, but after some investigation (thanks to your reports) we were able to determine that this isn't happening on the current build of the PTR. That's absolutely a bug and we'll be fixing it for a future PTR build.
Once the bug is addressed, this is what you can expect:
1. +Damage vs. Elites and +Reduced Damage from Elites affixes on items should work correctly against players.
2. The CC reduction rules that apply to Elite monsters in Inferno should also apply against players. Much like Elite monsters in Inferno, players will cap out at 65% CC reduction (with CC effects less than 0.5 seconds being ignored). These values are subject to change or go through different iterations as the PTR continues.
3. There is also an inherent 30% CC reduction in player vs. player which is not currently working on the PTR. So, a 4 second stun should only last 2.8 seconds in PvP combat. This can, of course, be combined with CC reduction from gear and skills.
(Note that pets are not currently considered Elite.)