1-Hamstring should be trainable before level 20
I don't care if it's trainable at level 10 or 19, but, a class that is built around melee range only not being able to play 2/3 of it's specs because it lacks the necessary tools to stay in melee range is absurd.
2-Shield Bash should be trainable before level 20
This one has as much impact on pvr it does pve. IMO it's more ridiculous that Shield Bash is not trainable before level 20 than it is to not have Hamstring trainable before 20. Warriors have zero anti-caster utility. As all ranged classed have a 40 yard opener that negates warriors only distance closer, you are left with running away to try and use los or getting shot in the face until you can actually make it into melee range. Now that you're there, you should have the upper hand, but, you don't have a way to keep the caster close (no Hamstring) and you can't do anything vs incoming spells (no Shield Bash.) Completely unacceptable. This is compounded by the fact that tanking as a warrior without Shield Bash teaches bad habits. Warriors should be learning that interrupting key spells is important, but, they aren't given necessary tools. If tanks had this early on then it would help create better tanks for the end game
3-Overpower and/or Disarm should be trainable before level 20
Warriors are touted as being the masters of melee, but, they have been reduced to three button mashing RNG scrubs. The incredible burst that end game warriors put out is resulting in nerfs being handed out that ultimately cripple low level warriors. So low level warriors now lack both utility and damage. Since the burst can't be added back, due to end game ramifications, extra utility is the only answer. I feel that both of these spells should be trainable before 20 since they address different aspects of melee pvp. Overpower allows warriors to catch up to rogues and hunters who always get to deal their damage first. Disarm takes care of the less evasive melee classes and is a great skill check ability.
All of these things are necessary for warriors to be remotely competitive. Hamstring gives all the warrior specs the basic ability to keep a fight in melee range. Shield Bash assists with the casters. Overpower helps in rogue and now hunter match ups (since int has been removed and hunters are stacking more agility and have increased dodge ratings.) Disarm helps the other melee match ups. To balance warriors with the top classes, distance closing should also be addressed. As I see it, it can be handled one of three ways.
1-Increase the range of Charge
2-Make Berserker Stance and Intercept trainable before level 20
3-Move Warbringer and Improved Hamstring to tier 2 of there repective trees (just kidding)
The most logical and easiest to implament would be increasing the range of Charge. Although I could argue that adding Berserker Stance and Intercept would be an excellent teaching tool for warriors to learn simple macros and stance dancing which is a requirement for top level play. Moving Warbringer and Improved Hamstring could have potential to affect the end game so probably the least likely to happen, but, this would give each spec a unique feel to them. That being said I think it would ultimately result in all warrriors going protection spec for the pure awesomeness that is Warbringer. So, I'll take that one off the table. The first two options are completely reasonable and combined with the changes mentioned in the first part of this post, warriors would be competitive again.