Although I'm a BIG admirer of the breen cluster torpedoes, they do set off a cooldown for the others. I worry that with 4 of them there's often multiple of them forcibly kept on cooldown.
I have two myself. But I think 3 might be your limit (45 sec cooldown on one launched, then 15 sec on others). This means that at 45 seconds, you could re-launch your 1st torpedo instead of the 4th (crude chart below).
Still, I suppose you can just sit there and spin around. I'm building to something like this myself and have been considering how many of each torpedo to load in.
the reason i have 4 breen cluster torps ( 2 front, 2 back) is to make sure no matter which way i'm facing the moment the shared cooldown is up i can fire at my target. i use 3 purple torp doffs and i some times have trouble because of the rapid fires, they're cooldowns get reset to global so often i am unable to fire the destabilized torp, just can't squeeze it in between the auto fire of the rapids reloads.
shield and weapon power are useless for me utterly, engine i keep low because of the current impulse engine being a combat impulse low which leave aux that i leave maxed. my gravity well ability ensures that the clusters, spreads and destabilized plasma are able to make full benefit of their aoe nature. feed back pulse is good for dropping their shields when the open heavy on me as i pop in and out of stealth to fire torps. i can fire all of the sci abilities stealthed so it's no worries. just that troublesome shield slot looking usless and can't seem to fill it.
Although I'm no torp boat pilot, I love my t'varo. Have you considered using the breen shield and replacing the engine? I would say get a Hyper impulse engine if you have the energy to spare. Maybe the aegis engine or an elite fleet hyper impulse engine. Or you could get the assimilated deflector for the massive boost to structural integrity and aux power boost and just use the breen engine and shield.
If your set on replacing only the shield I would go with the adapted maco for the placate proc ( not sure if it applies to cloaked vessels though), but if that's out of reach the jem'hadar shield is great.
Also, for your boff abilities I would say drop the engineering team for a EPtE. I say this because with two tac teams you will rarely be able to use the ET because of shared cool downs. Also, for science abilities you might want to consider polarize hull to keep a nearly 100% up time for most holds instead of the feedback or TSS.
For consoles I would say replace one of the armor consoles with one of your uni consoles. Put either a particle/graviton/stealth embassy console in with a +hull -Th.
You might also want to put a nukara web mine launcher on the back instead of one of the cluster torps.
Just my two cents though, like I said, I'm no torp boat pilot
What gives more damage? The 2p Breen for your transphasics or 2p adapted maco for your transphasics and har peng?
There is also the question that the Breen set gives a +30 boost to skill while the adapted maco is a % boost to the base damage.
Whatever the answer is, I think disrupter turrets in aft will yield some nice results with the proc going off. Doesn't matter if energy low, your firing fore most of the time, might as well make your aft do something. But if this is your preferred play style, but ignore me.