If anything, all these balance discussions are about the effect that defences can have on the meta.
Imagine a fantasy RPG where fire spells do more damage than lightning or ice. Because they do objectively more DPS, the meta is fire spells. So of course everyone stacks fire resistance. Everything becomes fire spells versus fire resistance until one day some sneaky notices the defence meta and wades in with a lightning build - he's doing significantly less raw DPS than his opponents, but with an attack they haven't made themselves immune to. This doesn't make lightning OP.
This is a noticeable thing in E

too - plasma accelerators in PvE are honestly not that great against NPCs and unengineered ships compared to just packing a cannon. Sure they're
good but they're not an absolute gamechanger, offering a decent damage/AP increase at the cost of power/distro draw. Solid but far from overpowered.
Since engineering came along and people started stacking upwards of 50% resistance to everything though, that marginal damage increase turns into an outright doubling. Now they're the hot must-have weapon, and it's purely because of the balance changes that have been made on the defensive side rather than any changes made to the weapons themselves.