So I have a theory :P
Guys that are good online don't do so well on LAN because online have different gameplay, mostly because [EDIT: on LAN] you are able to defend better and if you predict players movement you have 100% chances to aim properly. In order to win, when you play online you have to pick up items faster than your opponent and let aiming just do its job by instinct. I'm not saying it's not about prediction as well, and that on LAN you don't have to pick up armors and generally control the map, but compared to game on LAN, online style favours the guys with just better longer strafejumps.
Because for most players it is pretty hard to aim properly online, even from defensive positions, players are encouraged to play using the so called "forward tactics"-which mean no worry opponent might hit me, I will just run as fast as I could from one item to another, totally neglecting the possible position of my opponent.
It's like I just don't care where my oponent is, I will just do my runner runner tactic, as he won't hit me hard enough because ping.
For example, as prove to my theory I expect noctis not do so well at eswc masters.
But who knows, I might as well being wrong. And we'll see about noctis, isn't it ?