[QuantumDelta]

The reason why PromS is used (apart from it's milder weapon energy drain) is because of it's superior range and superior hull damage. The only (mild) unfortunate downside is that PromS fire travels faster than Kayser fire so unless it's a third shot the PromS doesn't benefit quite as much as it would, but the weapons compliment each other quite well regardless.

[deathfun]

Turn it up to Insane so you actually have realistic weapon energy drain rates and try the Kayser-Kayser.

I didn't know the difficulty affected how much energy was drained

That would explain quite a bit

[Androgeos Exeunt]

The difficulty affects a lot more things than you might realise. On anything above medium, you will seriously hate any warship with an LRed or larger mounted on it.