They will still be of use engaging targets of opportunity in our rear aspect when we're seeking out or lining up on targets in front of us - something which'll be of great use in fleet battles involving our weaker ships, we'll be better suited to help them without having to actually turn around and focus down on whatever target they're engaging.People keep saying they want the rear phaser for fleet battles, but that's the last place I'd expect to use them - any time the forward phasers aren't on a target, neither are the torpedo tubes, and we can't fire both the front and back phasers simultaneously.
It wouldn't be useless, but in a fleet battle we really should be relying on the rest of the fleet to shoot ships behind this one anyway.