Positron Def (EM), Combat impulse (Turn), Field stabilizing singularity core (SingS),Cov Shield (Pha for Mirror), Ablative armor, Diburnium armor, Field Emitter, EPS, Emitter Array, Inertial Damp (Couldnt find anything else on exchange), Singularity stabilizer.
I usually have more shield consoles in sci but like I said, non that were cheap on the exchange. This build has worked for all my cruisers for the other factions and I can tank great with them. Also all these are mk X green. I will move up to mk XI Blue at lvl 45.
Don't underestimate repulsors.. They may not be as powerful as they used to be, but they still do respectable kinetic damage - especially against larger targets.
Otherwise, my main guess would be you haven't compensated for their power difference. Warp Core potential and efficiency are very useful for Warbird pilots.
My D'deridex took an unbelieveable amount of punishment like a champ during the last battle of Devil's Choice(lasted long enough to get the command ship down to 20% without playing the kiting game).. I can actually charge right at those escorts and shrug off their charge-up attacks with the thing as well - as a science/non-engineer captain no less.