Warrior are great tanks too..
I was a warrior tank until now (still am, before saturday evening) but warrior is not very effective in tanking as you progress on end game.. Paladin has better survivability and with some skill and knowledge of your class you can hold aoe agro quite well. For example warrior just takes all hits like they are with some chance of reducing the damage from them ever since dodge got removed, warriors take like 30% more hits that aren't dodged anymore. Paladin takes full hits and stores most of them in barriers which can be nullified with a few skills. It's really helpful in tanking.
P.S. didn't take time to read all (did now) but yea, warrior is good at tanking, but paladin is better. Warrior is more of a dps class