I completely agree. I just came back from a 2 year LoL hiatus, but before that Twitch was always my favorite champion. I'm proud to have worked to get Whistler Village and Kingpin Twitch skins and coming back to find this nerf - I'm very disappointed. Twitch's play style has always been a skill-based glass cannon who can make amazing plays by stealthing in, applying DoT's and expunging. The reason the nerf is ridiculous is that Twitch has such a low caliber defense that the ability to E has always been the "reward" for getting close enough to the enemy who is beefier than him (which everyone is) and applying those DoT's before dying. Players were complaining about Twitch penta-killing with his ult (which I could see the argument for nerfing), but instead of addressing the complaint, they've basically decided to break his core means of damage and destroying Twitch's ability to effectively deal damage altogether.
From someone that used to play this game religiously , was happy spending money to contribute to the developers hard work, and was thinking coming back, I think the idea of coming back now is extremely doubtful for this reason alone.