To the OP. There is so much knowledge in the past few posts. Please soak it up like a sponge.
Also my main Damian is a tac in defiant. 3 dhc's 1 quantum and 3 turrets. I run 3/4 Borg set with aegis shields.
One thing I will say in slight conflict with a post earlier is to not sleep on the RCS console in a full on dhc build. I put one on and have never looked back. Who needs the +35 shields console anyway. (jokes) but honestly on my escorts I no longer run one. Just eps and rcs.
Also another thing to keep in mind is distance and the buffs your current target is running. I've seen my alpha go to squat when in 2 seconds my target went from no buffs to every shield buf imagineable. Saty way from targets that have extend shields on them.