If Ashe or Caitlyn is charging in at you and not immediately dying in a team fight, either you or your team is doing something very, very wrong.
1. They're fed and your team isn't, and you'd get steamrolled no matter what.
2. Your positioning is bad, and you're in front when you shouldn't be - you'd probably die even if they weren't Ashe/Cait.
3. Your team isn't focusing Ashe/Cait when given the sweet, sweet chance to - either they're bad, or somehow the other team has someone else more dangerous. In the latter case, that usually means that (1) is the real problem.
4. You're so underfed and/or underleveled that you die immediately. In which case, the Ashe/Cait is doing your team a favor by suicide diving you.