Sorry SE, but endgame won't work if you don't fix something.

[Dano]

Spells can be cast while moving if you trick the timer it isn't latency

that's the issue right there, the server still think you are standing still while you already moved on your screen, your position only gets update later. If so you happen to be within landslide's range you would have been knocked over due to positional not being updated.

it doesn't matter if you have a 3 or 4 second AOE window, if what's showing on screen isn't reliable/accurate you'll always get hit.