The issue is precisely that defense stacking is already out of control.
An armitage for example can pull 140% defense rating permanently and more if it uses a few extra defense enhancing items/boff skills.
Aegis 2-piece. KHG shield. Elusive trait. Atk Omega 1 (two copies for perma-use). 3 doffs of +10% def each when on recall. base defense @ high speed = 70%. Add it up it all = 140% defense. evasive maneuvers, +def granting items, etc... can pull it over 140 for brief periods.
@ 140% defense even borg elite npcs have a very,very high miss rate. Players? Tough luck you aren't hitting that sucker unless you snare him (but o wait! omega = snare immunity and chroniton/subsystem engine cant land a hit on it!).
AND if you put electrical tape on his mouth, AND if he is on crack and IF it was a Tuesday afternoon......
The point is, you are using a situation that is very uncommon as a reason to "OMG NERF!!!11!!!one!!1!".