Glacial Cascade and knock back

Some fancy dude told me if Glacial Cascade with knock back would deal more then 3 times damage to a single target which could be knock back，Is this true？ I can hardly test it on game.

Assuming a 100% knockback chance ands some increased knockback distance, that sounds plausible. Glacial cascade is not a projectile, but rather a rapid sequence of smsll aoe damage fields that slightly overlap with each other along a straight line. That is why both knockback and conc effect can provide crazy single target damage boosts. The same can be said about bladefall aswell by the way.

I was a little bit of confuse about the area of GC and its damage.Some claim you need increase area to increase damage,but you said cons would damage one target more times and do more damage.So should I choose more area or minimal my area so I can do crazy damage to one target?

A lot of people do both... increased aoe for clearing normal monster packs since you don't need as much damage to kill them and conc effect for massive single target against bosses.

Oh,then it seems I use GC + mine with +3 bow and empower was such a bad idea, I almost take every area points on passives along with carcass,so I will have damage as bad as I can have?I think GC maximal damage one target like 3 times,most of conditions it will damage twice.If cons will keep 3 times one a single target like always,shall I take off all the area points and carcass?Or shall I replace increase cirt with cons on boss even if it lower my damage on board?
ATM I have 50，000 or so on board and 68，000 or so after drug. but if switch increase crit chance I assume it will lower like 20% because I only have 40% crit chance on board with it,and my jewels are all crit damage.

To be perfectly honest with you, I'm only good at explaining the underlying mechanics. When it comes to min maxing your build to perfection, I'm pretty much the last person you'd want to ask. My builds are awful and suck big time usually, as I get bored of them before I even get the chance to perfect them. I aim for fun builds, not efficient ones, so I can't really help you with that one :/