Wouldn't be much (if any) use for PvP training. The thing that makes PvP more challenging is the fact that there is actually a brain (Even if sometimes that's not easy to tell 
) behind the enemy.
Guess your right there, though have seen some mobs use their powers far better then some players .
Tend to arena every 2 levels though to test new powers and there just isnt always a wide selection on people to fight against especially with this very annoying level bracketing. Maybe an idea would just be to allow players to set the exact level for arenas.
Gorgog
For the testing power-type implementation, there could be a gladiator "dangerroom" setting where, instead of your gladiators fighting for you, they fight against you and it could be used in solo or team mode. For some people it could be a way to practice, debt-free. Could be particularly useful for testing different powers and strategies on different enemies (thinking PvE not PvP of course).
I agree that the leveling bracket sucks. You should be able to customise the level more or if you have to have a level bracket how about auto-exemping or auto-SK'ing so people are brought to the same level like used in the zones. PvPing with someone 2 or more levels difference is no fun, I personally don't want an advantage I want a good fight.
Just a dream I know but with all the pvp starting up on test server wouldnt it be great if you could create "bots" controlled by the computer to fight for practice.
Could min/max them with any AT sets. If the devs felt that this would allow you to see powers you havnt gained access to yet it could be limited to sets you have leveled up, though it would be a great incentive to level up alts after seeing what some powers can do.
If the bots fought with as good timeing on heals etc. as tsoo sorcerers, for example, then they would certainly be very good practice for teams wanting to pvp.
Probably too hard to implement though.
Gorgog