Seems like most of the tier 3's have gone with missiles and railguns with an exotic weapon or two in the mix to spice it up.
As for OP weapons, i'd say as long as a weapon has a great build-up, people are fine with it and the weapon is grounded in lore. It can be pretty damn powerful.
Sure, the beam weapons on my ship is damn powerful, probably able to cripple a t3 cruiser with just a shot or two. But then again i'm at the max tech level.
So very powerful weapons are expected.
However, i won't be going around zapping planets with said beam weapons. That's just silly.
Since the destruction of some things are dramatic events. The destruction of a battleship, a planet, a star, a sector. Those things require some hefty cool things before i'd allow it if i were a GM.
Sure, a battleship would be easier to kill off than a star. So if i was the GM i'd let that fly with less of a dramatic build-up.
But i'm gonna confess, if a t5 civ attacked my character. Even if their coolest battleship is worse than the t3 cruisers. I'd give it a somewhat fair fight even if i brought in my character against it.
Since a battleship is such an iconic thing for a navy, especially if it's a flagship.
In such a case, i would forego logic and focus on drama. After all, it's no fun if the cool thing you brought get one-shotted in the initial volley.
But that's just how i roll in rp's.
Others will think differently. And act differently.