You must be close to the enemy. I think it works only against enemies, mines etc in a range <3 km. If it does, then you can see a tetryon beam that jumps from target to target. Actually, I have the feeling, that this skill is pretty useless.
It's pretty useless. It doesn't do much even fully buffed (pattern alpha, beta, omega, 125 weapons power etc...). Maybe if you use it as a finisher after an alpha strike, when the target is at 5% hull and unshielded.?
STO is the BEST game ever and the players absolutely LOVE it.
I've used it successfully, but very rarely. In the Vault Ensnared I flew into a group of ships while I was chasing down a vault weaver. EM was on cooldown and they were running circles around me. So I popped CSV II and the Tholian Rep power and boom- one banking pass and they're all fried.
I'm in an escort so it's pretty much useless. As mentioned above the range is ~3km. I might have time to pop it at the end of a strafing run, but I usually fire CSV and TS at ~8km (~5km by the time it triggers) and that doesn't usually leave much for the Tholian rep weapon to work.
I tend to get some alright use out of it for taking down fighters, swarms of frigates, and other small craft that are annoying. It can also be a nice way to stop a High Yield torp coming your way if nothing else is available at that very second.
So I would also not say it is "useless" but it is not that potent either. It is just a little additional damage you can deal from time to time. Sort of like "Why not?". If someone offers to pelt your enemy with a pellet gun are you going to say no?