Followed the invul guides and....
As Gospel said, in a set like Invul that starts with 0 Psi resist, it's pretty much impossible to get meaningful amounts without completely dedicating your build to that purpose. And since Psi damage is quite uncommon compared to other types, slotting for other types of damage mitigation (S/L defense most notably) does much more for your overall survibility.
Aegis is a good set for F/C defense, and is sometimes slotted for that purpose. But since F/C damage is also rare compared to S/L and E/NE, increasing F/C def is relatively low priority. (You'll see invul tanks using Aegis more often because it's a lot easier for them to soft-cap S/L and E/NE, once they've done that, slotting for F/C is more desirable.)
My Characters
Knight Court--A CoH Story Complete 2/3/2012
What Finduilas said.
I do like Aegis on my Mace/Stone to deal with the run speed issue, and finish out my Fire/Cold defense. However, on an invuln, where the majority of damage is S/L/E, those are the 3 types of damage I want to work on first, so I'll want to use a reactive over that.
I noticed that no one uses Aegies(sp) in their builds. I thought with the Psionic resistance it would be a great set. Cause originally I used it for temporary U. and Unyielding before Reactive armor took it's place.
Just curious.