I have to say, this idea did also cross my mind too.
Pricing it up, a 5-man Hellblaster Squad, with Primaris Master and Impulsor with the Shield Dome will set you back 344 points. This gives you 10 plasma shots within 41" (14" move + 3" deploy + 6" move + 18" rapid fire range if in Devastator Doctrine). The 4++ will give you some first turn survivability, and the Impulsor itself is a potent objective holder. Once deployed, you lose the 4++ and have to resort to embarking the Impulsor for more mobility.
By way of comparison, a 5-man Black Knight squad and Master wth Jump Pack will cost you 275 points, has that same 41" threat range (20" Turbo Boost, 1CP Speed of the Raven, 21" Plasma Talon range in Devastator Doctrine), same number of shots (albeit at AP-3 and not AP-4), and also has a 4++. You also have an improved melee profile if you need to charge into something to finish it off, and also benefit from T5.
In addition, if you're running around with Sammy and a Talonmaster, then there are more obvious synergies with Black Knights than there are with Hellblasters.
Anyway - that's my 2p on the subject. I've struggled with Hellblasters for a long time, but now that PA4 has dropped, I'm finding enjoyment and success with a Ravenwing-focused army.