I will throw it out to you in the way I am honestly thinking about it. I mean your trooper character is probably meant to be thought of as being among the best of the best. So I do. I think of him as a Spec Ops CQC trained soldiers. Thinking as to how such a soldier would think He would go to that close range combat more than other soldier. Play him with that mindset and it makes perfect sense to me. That being said I have seen alot of ranged enemies that do stay ranged and you can blast away and still tank at range just fine through alot of mobs. I wouldnt say all but alot.
Also.. I kinda agree. I think we should have acess to a different weapon as a vanguard. A shotgun to carry around would just make this class uber ****** even if it only changed the aesthetics of the class.