Is Protection Warrior any good in BGs/RBGs, 1v1, against healers ... and even in Arenas maybe? On paper it looks amazing but how is reality?
Also, does Defensive Stance reduces all damage (including magic) or just the psychical part?
Reduces all damage, but you're not going to have the amazing DPS output that it used to be able to throw around. Really a prot warrior is more of an annoyance than something to worry about, haven't seen many flag carrying these days to make a call on that.
I havent really done pvp since 5.0 right before mop came out, but prot was really fun imo in bgs. Even not flag carrying anything but defending a base in EotS having 2-3 different players get pretty crazy on you because they can't kill you and get tunnel vision as the rest of your team comes and knocks them off one by one. Second wind and defensive stance is a pretty fun combo. Then when they turn to attack someone else just stuns (Shockwave) or Int shout. I dont like pvp but doing it as prot made it fun for me. You wont add dps but its pretty hard to die.