Blademasters are extremily versatile, and can be good in the hands of a beginner and excellent in the hands of a pro. They can also be created to be the bane of any given race class if the player decides to go for a certain cabal/mastery combo. However, does this make them overpowered? I say no. The only two aspects I think are too buff is their offensive output with a two hander, and their massive race selection.
This mud is pretty damn well balanced and as usual a smart veteran will take a good race/class/cabal and beat down the vast majority of the pbase, but this does not make said class overpowered. Ogres recently got toned and I am glad because frankly they were the best choice for anything they could be, now it is not so clear cut. I think Battlemages are also extremily powerful but can easily be beaten by the same token. At the end of the day I think it really comes down to player skill and knowledge, not class imbalance.
Sure blademasters have a lot going for them but hell it's not like they are invincible. Between staves, scrolls, wands and consumables they can be attacked without being able to counter, spellkill, or snakespeed. It just requires creativity and patience. Attrition is really the blademasters biggest enemy. Even though they can in theory be prepared for anything that comes at them, they can still be caught off guard, in a wrong stance etc...
I cannot stress enough that player skill>race/class/cabal anyday. If blademasters are so damn incredible then why do people bother rolling anything else? The answer is simple, because they are not the be all end all, they can be beaten and there are plenty of other great classes to play that can be very dangerous.