And to that I must ask: leaving aside buffing the weapon (which is kinda outside the scope of the OP), how would giving a weapon an additional specific counter (since Hellfires already can be fooled by holograms) give the Hellfires a higher skill ceiling in such a way that it becomes more viable?
One thing to keep in mind is that if you are new at a game you don't know about how effective X is in most situations. You don't have to play in high level matches to learn how to properly deal with Hellfires. That is not to say the low level guys should be ignored, just that if there is a bunch of people who are saying that X weapon is not as useful as others then that must be considered as well.
Second, as mentioned there are already counters for the weapon. Not only the usual weapon counters (cover, shields, dodging them, which is not as hard to do as other weapons), but also the fact that they aren't great up close and the lockon can work on holograms and turrets as well. Also it is the only weapon which warns the player of an incoming shot.when locked on..
I don't agree with anti-missile turrets for the same reasons I don't want flares, it's another weapon specific counter that has no use for anything other than making a specific weapon less useful. It is otherwise useless if there aren't any nearby Bruisers or Rocketeers.
Furthermore, why should the solution to an issue like this be to buff the weapon but give it another counter? Seems more counter productive than anything.