Yeah, this is probabilities, but this is how you calculate % based stat however. Otherwise you are doing meta probabilities and so, kind of philosophy. And with 490+ SS, you'll don't have so much crit / det in 90 ilvl item.
Plus, ID vs Rear rotation is :
BS > TrS > SP > DK ...
vs
ID > ID > ID > DK ...
1) BS vs ID : 195 vs 180 = 15 delta. An ID crit will be 270. 270 - 195 = 75. 75 / 15 = 5 => You need 1 crit out of 5 ID for ID to be more DPS in a long time run. As you said, Crit is % so you need ~ 25% crit for it to be better which is impossible with a SS build
2) TrS vs ID : no debate. Ok, you'll gain more Tp buffering with TrS
3) ID vs SP: equal
So you win in fact one ID. Which brings you to the best rotation : BS > ID > ID > TwS > SP> DK > ... but this leaves you with only 2 sec left on GL3 to fade, so careful especially with OGCD skills delays (yeah don't speak about "off gcd" this is no real off gcd and you lose about 0.3 sec with them). I use this rotation for burst phase, Flank / Rear rotation for long time run (TP management and lot of moves ...). But in fact, this makes me sad TrS is not as good as ID. I think there could be improvement with this skill.