Energy weapons need
a power supply.
Preserve the power your weapons use while firing.
Most conventional energy weapons use Weapons subsystem power. That power affects their damage, and firing them places demand on that supply.
With other conditions held equal, higher actual power while firing means more damage from weapons that scale with it. Applicable firing-cost reductions help preserve that power and sustain damage.
Temporal Disruptors follow the same principle using Auxiliary power instead. [1]
Once you already sustain the relevant power at its effective maximum, further cost reduction may provide little or no additional damage.
What to check: Watch the relevant subsystem’s actual power while firing—not just while idle.
Sources & further reading
[1] Official STO: Rediscovered Event / Temporal Armory — confirms Auxiliary scaling and firing drain for Temporal Disruptors.
STO BETTER: Energy Basics — further background on power management.