sniper can be squishy but this remains to be a team game. It's a minor issue that can be remedied through composition or strategies etc if need be. Many of these melee heroes often uses these escape mechanism to initiation as well, which does put them in further danger. In doing so, they operate within a window of time where they have no advantage. Furthermore, nothing is also to say there won't be situations where escape is not needed thus making increased range more advantageous.
I'm not at all saying sniper is the hardest carry and honestly used him as an example off a whim.