Zed counters in LCS and the awkward spot they put him in
Zed's assassination pattern is all about target selection. He ults his defenseless target, combos them and gets out safely due to his double shadows. Against a team with low or unreliable CC, he will even do this 1v5. But no matter how hard this annoying technique demolishes soloQ, it'll remain relatively lacklustre in LCS. Here's why:
Probably his biggest counter. Good early base damage and will ult either his deathmark pop or the damage amp his ult offers. There's even an AoE heal to mitigate _his _AoE.
will rappel when he ults her. Chances are, she might even stun him in the middle of her team.
Free armor, double mobility (if you count his ult) and that stupid, unfair, Ihateitsomuch smokebomb.
Damage reduction and 3 forms of CC that will either catch him out or delay followup.
AoE damage reduction and targeted hard CC.
Scaling defenses and targeted hard CC.
Steals his AD and sustains endlessly.
Yeah good luck killing those.
So you can't even really lastpick Zed in pro play because he's getting teamfight/skirmish counters regardless. This leaves him with 2 targets, the ADC and the midlaner. The ADC gets pampered with wards and farm all game so he'll have a hard time killing that. The midlaner will play safe (with either TP, Exhaust or Barrier to discourage all-ins), farm with AAs and get every blue. And if there was a tower trade, he'll have a worse time splitpushing since he's more vulnerable in the longer lane.
All in all, this leaves us with a Zed on 2 opposite ends of the spectrum. Loads of catchpotential and excellent KDA in soloQ ... and in LCS, a Zed that can get a winable 1v1 once in a blue moon (and is consequently picked pretty much never). How do you balance that?