Pilums were not the only missiles that became overpowered with MS 10.
Well, that kind of illustrated my point, yeah. It's a matter of degree, not an absolute thing.
Pilums got a bit too good with the previous-version buff and regenerating ammo, anyway. If they were useful, unskilled, in outright killing enemy frigates by themselves, then that's performing rather beyond their intended role. Outright replacing Harpoons with Missile Spec is another symptom of the same - and, really, they could replace Harpoon Pods vs larger targets without Missile Spec.
I don't recall you changing Pilums' speeds when you buffed the missiles last time, though- just their hitpoints and damage. I could be wrong, I've slept since then
Anyhow, for Pilums, speed is extremely important; without it, they cannot catch certain ships before their motors burn out.
More importantly, in fleet actions, a slow missile is PD fodder. 20 of them, 40, it kind of doesn't matter, once speeds are low enough- AOE PD eats them much more easily then.
And nobody was saying, "a single Pilum is a frigate killer" here; the issue, with any missiles, is "what happens when you can bring 4+ launchers to bear on a target", because that's when things start getting weird.
A single Harpoon Pod is not a real threat to any Frigate with shields, unless it's absolutely Flux-locked... 5 fired at a Frigate, with Missile Specialization 10 is dangerous, because that may push even a zero-flux Frigate into Overload... and 20 is enough to kill a lot of Cruisers, even without Missile Specialization 10.
Missiles scale very differently, because they're alpha spikes and even against an Onslaught, it doesn't take more than two to clear the armor blocks- and then the serious damage happens.
If missiles that actually work is a real issue, but they need to work in order to preserve the feel, why not simply make PD work better, to preserve the other part of the feel, i.e. capships that don't really care a lot about anything that's not a torpedo?
That's another option that works, and it doesn't need to be a DPS buff; an OnHit() projectile / beam buff against Missiles as a class is straightforward. That's how I ended up dealing with this in Vacuum, the last time I went down the rabbit hole. Honestly, though, I think I'm getting close to having all this mess balanced over here; it can be shifted (for example, doubling all the missile timers, to feel more like 0.65) without ruining missiles in their special role or needing any of them to have ammo limits, too; the issue has always largely been balancing missiles against each other for OP costs while leaving them functionally able to do what they're designed to do, rather than trying to compare them with anything else.