I'm playing BG for a while now, and I recently stopped playing it for the moment considering how poor he was in 6v6 setup.
That being said, the 3 main factor making it too weak are the comparison with others tank (moral pump, utility) the outshining comparison with mara (mara bringing a better version of nearly everything a BG can bring) and aswel the broken career trees.
In order to be effective, as a 2H tank, you need CD and you need the parry tactics, you can manage to get both but you need so much sacrifice for that, full mercenary to get the extra point and you skip everything but those 2 skills... and the result isnt that bright, you just a sub tank in a grp, a wanna be dps.
Career trees has to be reform, giving access to the parry tactic earlier otherwise you cannot mitigate enough guard dmg. Doing so, BG can invest more career point in order to get all the tactics set and ability he needs, atm being viable 2hander requires way too much sacrifice :
http://waronlinebuilder.org/#career=bg; ... ;;;0:0:0:0:
A KD (3-4 sec not 5) requiring parry instead of block would be awesome and much more reliable. Others tank uses block to moral pump and BO got an amazing assist dps while being kinda defensive thanks to that. Making BG a parry based tank would make that career unique and interesting. And I'm sure any snb BG would see a parry based KD as a buff as well.
We could aswel nerfing a bit the mara's armor debuff and put that role into BG's hand, his armor debuff isn't that far from it atm when you spec full Malice. If you give the current mara's armor debuff to BG and vice versa, BG would have a specific role in party, same as IB had in the double slayer meta. OR we could just buff the BG's armor debuff and let the mara's alone for the moment if asking a nerf creates too much waves atm.
One thing for sure, noone would choose a BG over any other tank in the current state of the game. And nothing will change until we deeply look into his career tree and fix that mess.
For me his role has to be 2 hander, I cannot see how he could compete with a snb BO no matter what change you make (BO dpsing more, more def, and moral 4 after 1min or so), if the BG is snb, he would have to bring so so much more utility in order to find a spot in a party, at least with 2 hander you COULD get a huge part of utility with your assist dmg.
If I repeated what others said I'm sorry, and if the way I put things doesnt fit the rules I'm sorry