Shield damage reduction does not have DR. It is multiplicative. So at 100 shield power, your shield should take 20% less than it did before. But since shields scale so poorly compared to weapons, well, it won't fix the issues with the rampant offense in T5 PvP.
All Resistance has Diminished Returns. So if you're equipping armor already ... that shield bonus is ... less than impressive.
Tricobalts at close Range do insane Damage. Also they dont show up in Combat log very often. Some days ago i got hit by one with 100% Shields + RSP ,100% Hull + HE (making up for around 45% Hull resist) and got onehitted by this Torp. Damage didnt show up on Combat log or above my ship. (Talked with him after the game and he told me those tricobalts can crit for ~130k damage at exposed hull ,thats even enough to take out shields + hull on most ships even with resists)
RSP does not affect projectiles in any way. The damage a projectile would do to your shields will be the exact same with or without RSP. Just wanted to point that out.
Diminishing returns doesn't make as much sense when applied to offensive buffs. A simpler and more elegant fix is to restrict stacking of certain abilities completely (which I suppose you could call 100% diminishing returns if you really wanted to). Attack patterns are the worst offender and the most obvious example of a group of skills in which at most one power should be active at any given time.
Nerfing the stacking of AP:Alpha, Beta, Omega will probably defang the worst of the Escort damage problems all by itself. They shouldn't stack. They should never have stacked. It doesn't make sense from a 'lore' perspective that they stack, and it's clearly broken from a balance perspective.
Easy fix: do not allow Attack Patterns to stack. It doesn't even make sense that you can use more than one, given what an 'attack pattern' is intended to simulate.
AP:Beta and AP:Alpha together contribute most of the ludicrous damage.
Yes tactical should be punished for using their career skill along with a BO skill. Let the other careers stack their skills to make up for Tac being all-powerful and maybe people will stop complaining? Ohhh wait people never stop complaining. My mistake.