High yield is a modifier, click it once you get the mod, click it again you just put the same mod there, (your not getting two, just resestting the first one's time until it wears off)
As for the Emergencey to shields idea, that provides a insta-heal and power level boost, clciking a second one applies its effect, shield heal, and the same power level, (you dont get two boosts of power levels, just the same one that will now last longer)
A solution to your problem would be to use high yield, hold your torpedo fire, fire at opportune time then use yield again
Or just use one high yield and get an attack pattern skill in place of the copy :p
i'm just now imagining the OPness of BO3 fired inbetween 2 seconds...i mean it is possible now, just needs a little practise.
but having torpedos fire directly after one another doesn't raise the total DPS, since the CD raimains...it would just be more bursty.
And with a little timing it can be done with the current system anyway.
preload HY, wait 15 sec...launch torps, activate second HY...wait for the tube to come online again (3-5 sec depending on type and DOFFs) ...fire again.
If you use 2 torp tubes you only have a 1 or 2 sec window to activate the second torp ability, but still doable.
only one torpedo is fired in high yield 2 and the second high yield 2 'charge' vanishes.
You are doing it wrong. If you cast THY, then cast it again, it doesn't stack to give Torpedo Higher Yield or Moar Torpedo High Yield. It just recasts the buff that will be expended when you fire the torpedo.
How to do it CORRECTLY.
1. Cast THY.
2. Wait For THY to nearly finish recharging.
3. Fire Torpedo.
4. Cast THY again.
5. Fire Second Torpedo.