Deepstriking suits is not always ideal as a bad reserve roll and you are missing a lot of firepower.
By attacks per turn I assume you mean close combat as Broadsides only fire their railguns once but do get the reroll to hit. The targetting array also only boosts them to BS4 meaning 3+ to hit without a markerlight to support. If you take a targeting array, you cannot take the multi-tracker forcing you to choose which weapon to fire
I tend not to use broadsides for anti-marine use unless I want to pop a character. Anything T5 or lower is instant death so can remove a hard target fairly easy.
For anti-marine work try the FireKnife Crisis Suit combo of Missile Pod, Plasma Rifle and Multi-Tracker. Can move 12", fire both weapons with good range and then move 2D6" in assault phase to get into cover of our of range of return fire. Have a couple of shield drones on a hard-wired drone controller to absorb incoming fire with their 3+/4++ saves and you have a squad that is hard to catch and fairly difficult to kill.