Against good Hashashin you will win no more than 3/10 times. They make a lot of desync, they are fast, mobile, a Paladins on steroids. They are also partly imune on grab, will using that jumping skill with two charges.
You can do only two things vs tham - a PERFECT timing, and actualy using that desync vs tham.
Now, how? For timing, trow spear in the moment when they summon tornado, that skill dont have super armor, and its bad for there line of sight, as it is bad for yours.
Also, when they enter in that Void Knight like charge skil, dont attack tham, they have iframe will in that skill, but the moment they attack you, it becomes super armor and you can grab tham.
Do not try to grab tham will they jump, they are imune during jump, but they are not when land, and have little delay, so grab in that moment.
Do not use Shield Charge as you normaly would, you will fail, try to use it as a Shield Counter, it gives daze.
As for using desync agains tham, you just need to move fast and hard to predict around tham, when they start moving around you, and just catch tham in animation, becouse they are use to dance around you but not another way around, and you can use that to confuse tham.
But again, chaces are not on your side.