Examples of things I personally feel are well designed and thought out procs?
Well... enforcer absorb procs, martial artist damage and crit procs, enforcer and soldier AR procs, meta-physicist init and damage debuff procs.
Off the top of my head.
NSD proc is over the top no matter the duration to be fair.
I feel for agent snare procs, unbreakable but stim-able would be a easy pick.
The mentioned root/snare/stun resist would be a pretty nice proc as well (random Unhallowed Force proc would be amusing).
A defensive proc that has a chance of breaking all agg from you for a second or two without clearing hatelist would be something quite nice I think.