Your question doesnt make much sense or needs to be elaborated on;
The base damage for all beam types are the same apart from AntiProton which has stronger crits. So your loadout of 6 beams and a torp will generally hit the same regardless of energy type.
As a cruiser you have to accept your damage output is not going to ko anyone. therefore you should decide on a energy weapon type that compliments your ship build (or team focus).
If your looking to dps more than support, then go with either AP or Phasers, disruptors will only really be worth it if you are running in a team who all use disruptors thus proccing the targets defense to hell allowing for easy kills.
I personally feel the best bet is to go with one of the hybrid energy types, you lose a little dps overall but the benefits far outweigh this small loss.
Pol /Tet << I run a drain build and therefore these with omega XII space set works amazingly
Phaser /Tet << These are VERY deadly in the right setup.
You mentioned whether your power would be effective, what are you asking? your wep power levels or dps output?
Either way, your dps isnt going to be escort like, your power levels must be regulated well when broadsiding your enemies, I suggest, wep batt, energy siphon or emptw.
on a assault cruiser are disruptor beams good to have on a ship 3 for and aft with quantum launchers. will the power be effective with this weapon set up.
The simple answer is "yes". The disruptor proc is pretty consistent in the damage boost it offers. The phaser proc can be the most lethal if it hit's shields or engines but it's not good to count on a proc that rare and antiproton's bonus critical damage is only good if you built to maximize crit rate.
The disruptor proc does not stack unless something has changed since I last checked but even one application of -10% resist can make the difference in you and your team's DPS to kill a hard target.
For PVP using disruptor weapons with multiple [acc] modifiers on them will help your team on focused fire kills more than any other energy type.
Check out the "dragon build" thread for the basics of good cruiser Boff powers. Part of contributing damage in a cruiser is cycling EPTW1 and EPTS2/EPTS3 for a constant 120+ weapon and shield power setting.