Here is what i run my tac based Vor'Cha refit currently with:

Weapons Front:
2x Single cannon
1x Dual heavy cannon
1x photon torpedo

Weapons Aft:
4x Turret

Assimilated Deflector
Aegis Angine
Reman Shield, strangely this works better for me then the aegis shield or the borg shield

Devices:
Subspace Field Modulator
Shield Batt
Aux Batt

Engineering Consoles:
RCS
Field Generator
Weapon Power
Neutronium Alloy

Science Consoles:
Assimilated Console
Induction Stabilizer

Tactical Consoles
3x Prefire Chamber

BOFF skills:
Tactical:
TacTeam1
Cannon Rapidfire 1 or Cannon Scatter Volley
Torpedo Spread 1
Science:
Polarized hull 1
Hazard 2
Engineering:
Eng Team 1
DEM1 + DEM2
EPTS3 + EPTS2
PPTA1
Aus2SIF3

i have a single cannon vorcha and im pretty happy with it. the best part is whenever your opponents arnt a bunch of escorts you can swap in duel cannons for even more damage on the slow movers, something an excelcior cant do.

I personally think you should replace the Aegis deflector with an assimilated one and the assimilated shields with a covariant (Aegis or some such). The Borg shield just doesn't have much in the way of capacity (much lower then an escort with a covariant) and while you will be able to recharge it, it does make your shields rather brittle to high sustained DPS.

While it has an ever so slightly less hull, I'd say a Vorcha is more survivable due to it's manoeuvrability and engineer BO slots.

If your running shields at 50 get a +7 to shield power thats 24% regen.