actually had enough coms on my sin to buy the relics. Did two 10 min parses with the internal and two 10 mins with the kinetic:
My stats (running balance): 37.57% melee crit; 36.48% force crit
Internal proc: ~22% crit rate
Kinetic proc: ~18% crit rate
Difference is probably RNG.
I did parses with my gunslinger both in dirty fighting (high bleed crit rates) and SS (no bleed benefits) and it made no difference ... 39-43% crit rates.
I'm starting to think it's based on tech crit chance on melee crit chance like I had originally proposed. So all force uses are disadvantaged.
Just need a trooper/BH to confirm.
EDIT: Found a commando on torparse using internal proc relic. Crit rates are 30-40% for the most part. Have no idea his stats