Well, i really like the Heavy Bolter and i thinks its fine. The Problem in you video is that you just use the Leftclick at max-medium range.

The Heavy Bolter is by no means uselss, its one of the most, if not the best dps weapons if you hit more shoots on Flesh Targets with the Leftclick (so you need to go closer)

The problem is that you really have to "gear/skill" for it to make full use of it. You can have -Spread on your eye implantat (that helps a lot) and you need to go a lot closer and it needs some time to do full dps so you need to go a bit tanky.

This weapon is very "special" so its very subjective if you like it or not.

I would call your description(and the video) not a bug, especially when you shoot at a very far distance and you have some obstacles that makes the precision even worse.

Yha fo a heavy weapon its is  useless  right now.  the hailstorm is the only on thats  worth it  to me and that doesnt make  me  want to use a gun for  hyst that ability.

It's almost like  when you fire    your shooting in a cone not a triangle  so  to many shots go up and down  the   just left to right.  hit rate  like 15%

Also note the  engagement range in the video is  not what a rifle should be.   That is the same range as what hand guns.