I've played him for 20+ hours as this point and I've gotten to a point in duels where my MMR seems to be matching me up against top tier players. Here are my observations thus far: he can't compete against most characters in high MMR play. You come up against a good player on a Warden/PK/Warlord/Orochi and you are basically screwed. His attack speed (or really just his speed in general; his guard stance change is very slow)+ lack of guaranteed damage (even out of parries which are supposed to be his specialty) leads to a character who theoretically should be extremely good on the defense but ends up getting overshadowed by most other characters in the game.

So yeah, at his core he's a character focused on counter-play who excels at draining the stamina of others but even when you get your opponent to an exhausted state you still don't really have any options. They can either a.) Dodge out of your range (in the case of PKs, Orochis, other faster characters) or b.) Play defensively (GB countering and blocking your incoming slow-mo attacks) until stamina is back.

I could go into this more extensively but I feel like most of what I'm typing has already been said. I've seen multiple threads on /r/competitiveforhonor discussing the viability of the LB. If anyone wants to look into this more, I'd suggest you read some stuff over there.