DG support vehicle/ walker: Helbrutes vs Blighthauler

[Plaguecaster]

I was looking for people's opinions but generally I tend to run a infantry based force with a few FW walkers in support of my plague marines and poxwalkers. At the moment I am running a blight hauler for each Plague marine squadmainly for the cover bonus as having my plague marines basically having terminator armour due to the aura from the haulers is quite nice, however I also wanted to include them to add some extra ap in the form of their multimeltas and missile launchers. Unfortunately since I solely run them seperately with 1 hauler per plague marine squad they tend to have miserable luck actually hitting anything only hitting on 4+. I was just wondering if anyone else had any luck running them as a single hauler or would I be better off swapping them for a helbrutes with missile launcher and twin lascannons as whilst they may not be as durable they would have a better chance at hitting stuff since most of my list struggles to deal high ap damage at long range (Butcher cannons are mostly my only long range weapons but they are only -1 ap so I can struggle against high armour targets)