Torps, sadly, are pretty useless in PvP outside of escorts. A slither of a shield will prevent it from hitting the hull, rendering it's burst damage non-existent. Given how over the top shield tanking is in this game, chances are there will be a slither of a shield by the time your torp gets there.
Then you have the kinetic resists, which can make torps so pathetic that a single DHC shot does more damage.
Trust me, I've tried to make them work on a cruiser. I've used the generic torp setup (6 beam, 2 torps) and a more escort style build (3x dbb, 1 torp, 4 turrets). While I've managed to get a few hits on the hull, it's just not worth sacrificing the sustained DPS that 8 beams give you, for a few lucky shots. Chances are, even when there is a shield down, the teams escort will finish it off with it's DHC's before your torps even connect.
Even with 8 beams, you'd have a slow hard time getting someones shields down. 8 turrets, not a chance, they just don't do enough damage.
Like others have said, torps are next to useless given how common shield healing is. Beams on the other hand, can still do decent damage against hull. In a cruiser you don't have many options for bursting down enemy shields, so the absolute best damage you can do against shields is by running 8 beams.
Yes it's lame, and yes it's not Trek without the torpedoes, but torpedoes just aren't very good weapons.
I find torpedoes work best on escorts (they can aim them easily and have other weapons to burst down shields) and shield-stripper science ships (they tend to run low weapon power, but they don;t need their beams to remove shields).
Against NPCs, torpedoes are just fine, because NPCs don't heal themselves.
I'm a Tac in an Excelsior retrofit and the weapon setup 4 cannons plus 4 turrets is astounding and yes, DEM III seems a great skill for it, but I also add a TB to slow down the target before it runs away...those little pest klingons...
Currently levelling a Vor'cha to test that build there.
I have seen your Vor'cha yesterday in a C&H and I have to say the bleedthrough does hurt but (at least for me in my sci/sci) it has never been a real danger... at least on its own. Having already lost half your hull when an escort is ripping through your shields on the other hand is extremely unhealthy.
Did you ever thought of adding a Peng to your build? I know it is currently frowned upon but as soon as it is fixed it might be a nice way to further increase your bleedtrough with some spike dmg via the secondary explosion. If it is worth the lose in constant dmg is up to a test.