Probably has been done already but here is my attack.
This shows the Average Damage on an eth thresher insight comparing min and max roll %ed and critical strike.
One can see that a 5 and 6 cs 200% Ed Insight outdamages a 260% ed roll with only 1 Cs showing the importance of the CS roll on insight.
Eth Thresher average base damage : 114
Critical Strike 1 - 6 Chances to double damage : 1.16 1.25 1.32 1.38 1.42 1.46
200% ed roll average damages cs1-6: 396 427 451 471 485 499
260% ed roll average damages cs 1-6: 476 513 541 566 582 599
Please double check the numbers