There
is this thing called 'prediction', you know.
In case that wasn't clear enough, I'll outline the steps:
1. Using your eyes, find out what enemy champions are within the area.
2. Remember what their skills do, and the general ranges of the same.
3. Remember (or, if you don't know, guess) on what occasions they are likely to use those skills against you.
4. Play normally, positioning to avoid being threatened by enemy skills.
5. If the enemy makes a play or you find yourself out of position, refer to 2 and 3. Consider three situations:
i. Enemy will not be able to take advantage of their play or your mistake. Walk clear and revert to 4.
ii. Enemy will be able to take advantage of their play or your mistake. Continue to 6.
6. Given the enemy list of skills and their ranges and effects, estimate the likely positioning they will use. See subheadings:
i. If your E directly away from the enemy will take you outside their effective range, do so.
ii. If if will not, E laterally or diagonally (depending on terrain) in the direction you least expect the enemy to use their skill towards. Continue to 7.
iii. If you are following ii. and there is a jumpable wall in your immediate area which would separate you from the enemy while also avoiding their skill, E over it. Continue to 7.
7. After using E laterally or diagonally, move away from enemy and/or towards teammates, or use your own skills against the enemy champion as the situation dictates.
Was that sufficient? Because sarcasm aside, the cast time isn't exactly a Fiddle ult. Take bot lane as an excellent example: unless you wait to E until that Blitz grab, Thresh Hook, Zenith Blade, Crescendo, &c. shows up on screen, you're fine. It's not the fault of the champion or the game if you play reactively rather than actively, responding to enemy skills rather than predicting when and where they're likely to be used.