you will - try it for your self get 35% crit use the rotation Plasma Brand - Strike - Sunder - Overhead strike - Blade Storm - Sunder test for 6 min 3x you will find you dps output is within 30 dps each test if you do it correctly (not using masterstrike avoids the influence of proc chance). Then lower you crit to 32% and test 3 times for 6 min same simple rotatoin. you DPS will go up.
if you spec Inisght only 1 point instead prefering Momentum you will find 34% is best.
As you say this is to do with the value you get from specific skills critting vs the blanket value of damage increase from power. Its the same with Sentinals - all the best ones spec 30% crit not 35%. crit and power are not equivalent in all regards except for the diminishing returns of crit as you claim - although im sure this is by far the biggest factor. you do say this your self in your post regarding force sweep so im not sure what else to say.
That level of crit may very well be optimal, I'm not disputing that. I'm just saying that if that is the case at campaign/dread guard level, then whatever amount of crit rating gave you that would be roughly about right at Columi/rakata level, and thus its easier to just quote the amount of crit rating that gives you that crit %, instead of telling someone in lower gear they need to get to a specific crit%, which would cause them to over itemize crit.