See my post above about crit rating, it appears like elemental is for force users and internal is for tech. I'm not 100% sure, but you should take it into consideration before getting one relic over another.
As a Watchman Marauder i can affirm that Internal relic has around 15-20% crit chance, and elemental one has 40-42% crit chance, as I have 41% crit force buffed, i assume that your statement about force/tech users is correct.
So for force users BiS should be:
1. Dread Guard Elemental Proc Relic
2. Dread Guard Relic of Boundless Ages