Well a couple things. You should die pretty much instantly to an assassin if all you are building is damage. That's the point of assassins: to take out the high priority targets. Also, Ashe probably has a low MS (don't know for sure, don't feel like looking it up) because she has a built in slow as an integral part of her kit. I'm taking this from other board posts I've seen, but the reason that the whole mobility creep started was because Ashe had a toggle perma-slow that she couldn't miss, so the only way to catch her was if you had gap closers. Ashe is the kitting queen. She has one of the highest AD carry ranges (something in the 700s I think), and if you know how to kite efficiently, she is still pretty much uncatchable. I'm going to try and find a video where Ashe kites the hell out a Gnar and (I think) a Ryze, killing both of them with ease.
Granted, she could use a new passive, and maybe a different E (the gold income is probably because she is primarily a beginner champ, so having extra gold really helps). The vision thing should stay though, as it fits her lore, and is really great utility.
EDIT: here is the video: http://youtu.be/Q0vk66t7kNo?t=18s It was a Gnar and a Lee Sin, not a Ryze. She does use flash, but that is to dodge Gnar's Crunch/GNAR! (she also uses her heal, but she is fighting 1v2 against a tank and a fighter, so that's to be expected), and she never uses her ult.