Pay to win = Being able to acquire any gameplay benefit in game through the use of real world currency. Cosmetic/Vanity items are not included.
WOW = Nothing except vanity/cosmetic is buyable with money (Not P2Win)
D3 = Everything you could possibly want is buyable with money (P2Win)
SWTOR = If you can get xp bonus, currency or equipment/items with more than a mere vanity/cosmetic use, it is P2Win)