Um, what's a Varon-T disruptor? X( Plus, until STO, I've never seen the Federation use disruptors at all. Just saying. XS
Unlike the regular disruptors which are effectively less utilitarian versions of phasers (tending to have Stun and a selection of high power "kill" settings) the Varon-T disruptor vapourises the target from the inside out resulting in a slower, agonising death. Given the way it was portrayed in TNG it is possible Kruge in Search for Spock had a weapon of a similar nature. Only 5 Varon-T's were ever producted, they are notorious and largely outlawed.
Thalaron technology is banned in the Federation because of its lethality, the Klingons consider it dishonourable, and anyone in their right mind wouldn't touch it with a barge pole for fear of having one, or all, of the major powers breathing down their necks asking, "what the hell do they think they're doing?!"
Yeah, Thalaron weapons are kind of Star Trek's example of "Even Evil Has Standards"
Something so hideous that not the Klingons (who aren't evil so much as a Orange/Purple morality) the Federation, the Cardassians, most of the Romulans, etc. wouldn't use them.
Besides, could you even get that effect to work in a beam, either on ground or on a ship? The way it works with all the particle thingies suggests no. That's why its a thalaron mine and not some other kind of weapon.
To be fair, my recommendation is "avoid." Largely because if we get 'em, they bad guys get 'em. I've been having enough issues lately with the unholy combination of Centurion Engineer dropping thalaron drones like candy, and medic of some sort busily healing the engineer. You aim for the medic, the engineer gets you with the thalaron mines (BOFFs really aren't good enough to avoid them yet.) You aim for the engineer, the medic heals him and you still have to dodge thaleron. Same result. You aim for the drones, and you get into a vicious circle of kill drone, another pops up, and you never have time to burn one of the two down.
I would imagine that the final take from the "Cloaked Intentions" series is either a Romulan or Reman Bridgfe officer. (Although come to think of it, I never did get my Breen Bridge Officer) or something else innoculous like that. Thalaron weapons just too big, mean, and nasty to put in game