I'm expecting more of the same from Gunbreaker when it comes to tanking.
I think Gunbreaker might be faster than other tanks.
Ammo used to perform defensive cool downs and boost damage of certain weaponskills.
In the trailer you see the Gunbreaker shoot into the air and a shield covers him. Near the end he performs one weapon skill followed by a jump into the air, pulls the trigger, and then slashes down with a blue lighted slash. This could be an oGCD or boosted weaponskill.
I kinda hope we don't have a "Reload" ability like that of MCH. Although as long has GNB, I like GNB better than GUN, doesn't have to deal with random procs a Reload command might not be so bad. Thinking about it you could end up where your definsive CDs still work like normal but if you have Ammo loaded that will boost them but not be required to work.
But here is what I think we will get. 1 Enmity combo. A oGCD DoT or a a DoT combo. A DPS combo that you are going to want ammo for. A few defensive CDs that may or may not require ammo but can be boosted by it. A few oGCD DPS moves like Spirits Within or Carve and Spit, or is it Carve and Split... I don't play DRK that often. These may or may not be boosted by ammo. One or two AoE attacks. Maybe one that generates enmity and one that is for DPS. Again maybe boosted by Ammo.
Now here is the real question. If we do have an ammo system that we have to constantly reload, will it be 3 shots like MCH or 6 since most of the gunblades we've seen have revolvers on them which I "think" normally has 6 shots?