This gun is really cool and imo - it should have +20-25% chance to use Bursting Round, same as with other 2h weapons, like these ones:
Ugdenbog Boltthrower
Messenger’s Repeater
Bile Regurgitator
Mythical Valdun’s Rifle
Mythical Portent of the End Times
(And some other ones, but I think you get the idea)
For some reason most of the 2h guns, even MI ones, received new FoA tech with increased %chance to use, but Desolator was forgotten and currently just not a good pick for a main weapon slot.