Hate to break it to you but if you are tanking as a warrior and still losing hate to everyone then its quite possible you are the one at fault. Also if the player is level synced from level 50 your gonna have a hard time keeping aggro as they are going to be able to do the best damage possible for that level. Most of the time if im going on my monk, i let the tank know i will pull one off of him and tank it so he doesnt fret about it that much. plus it helps him control the ones he/she can take care of at lower levels. Tanking is really easy once you get Defiance (30) as war and Shield oath (40) as pld. You should already have defiance from your warrior job. if you dont then you need to get it ASAP. and if you are still losing hate you should take a look at a guide for warriors. they are easily the best AOE/Solo emnity tank due to the high damage (pld is for defence buffs so dont get butthurt i said this k guys ;D) If you let people know to slow down and take it easy at the start runs go a lot smoother.

Many people have the idea that tank is group lead and sets the pace so make sure you tell them if they are pulling hate off of you and ask them to slow dps if needed. If they still dont listen then screw it, theres nothing you can do to change a bad dps, besides kick them ofc. continue tanking as you would and let them eat it once or twice. they usually get the hint.

So in short:
1. Get Defiance
2. Read a guide.
3. Use OP/Flash multiple times at the start of a fight to build aggro on the targets.
4. Use your Butchers combo a couple times on the enemy being focused first, then rotate your first 2 skills on one target, then butchers the next one. I do this and rarely have issues with aggro on multiple mobs of ~3.
5. Relax, its just a game and people will ALWAYS be dicks online. its in their nature to when they have no serious repercussions.