The problem with beam arrays, are that they cannot be linked. There should be just way to shoot one beam instead three with 3 beam arrays, if you link them. You would have reduced chance for procs, but increased base dmg, hence higher crits.
It makes sense that such powerful beam weapons will drain energy out of the weapon capacitators.
What does not make sense, though, is that there are weapons (all types of cannons, most notably the DHC's) for which this is somehow not the case, yet they do even more damage. WTF.
actually that makes perfect sense. Cannons utilize short self contained highly charged intermittent bolts of energy. As such they do not drain as much energy as Beam Arrays which use highly charged continuous beams of the same kind of energy. A Continuous beam is always going to be a larger drain on a system than a short intermittent bolt of energy.
I mean there is a reason that Sub Machine Guns are still the weapon of choice in this day and age and not Directed Energy Weapons which do actually exist in this day and age but which are so bulky as to make them unwieldy.
Over the course of 15 seconds, DHCs consume 60 power (12 per second for 1 second per firing * 5 firings) and generate what we will call 1X damage (at mark 1, 188 damage * 2 shots per volley * 5 firings = 1880). A beam array consumes 120 power (10 per second for 4 seconds per firing * 3 firings) and does 0.63X damage (at mark 1, 100 damage * 4 shots per volley * 3 firings = 1200).
In other words, a beam array consumes twice as much power to generate around 2/3 as much damage.
Your argument is that because cannons buffer their drain with capacitors, so are not as hard on the ship's power grid and that's why they don't drain as much. The problem is that cannons don't drain power all at the time, only when they fire, which leads to them being ridiculously more efficient despite the whole problem of adding a level of capacitance, which would not be lossless.
This is all kind of moot though since the way STO's power mechanics work makes no sense as a whole because weapons "refund" their power at the end of their firing cycle. The total effect is to model a system with infinite power output but only limited transmission such that multiple simultaneous devices can overwhelm the transmission grid. If that were the case, the logical conclusion would be to build your ship to have only 1 weapon connected directly to your infinite power source, and that single weapon would be a beam whose constant throughput is only limited by the melting point of the systems involved.
Nothing about the weapon power situation makes sense, either with our physics or with theirs. *shrug*