If you're vulnerable to everything from both the ADC and support, you're either positioning flatout wrong or not waiting on your support to initiate the level of aggression you're trying to do. The first is solved by stop doing that; the second, by learning when your support wants to do that level of aggression and following his lead better.
The good twitches I've seen tended to avoid trades, and go for all-ins at strategic moments, where Twitch's burst is actually higher than most ADCs, due to how Expunge works with his kit(and that all his burst is tied up in that one skill).
#assassinproblems
The challenge with watching LCS-level play is that you gotta realize, not only do they "know their burst", but they also farm better than you. Completing BoRK 2 minutes earlier opens up kill opportunities that I'm just not capable of taking because I'd be sitting on Cutlass+2dagger.
He actually doesn't reward generally aggressive play like...Caitlyn would. He rewards *TIMED* aggression very well, though. As in, its less about how frequently you trade and more about the fact that they're probably dead or backing every time you do find a good trade opportunity.