look, i'm well aware that bot lane is 2v2. but there's no point in taking that to account because the supports you choose for each carry is totally arbitrary and are matchup altering in themselves. so if we try to make an example of a realistic bot lane and say that maybe ashe is supported by thresh and vayne is supported by morgana; and that matchup would quite likely swing in vayne's favor. but that tells us nothing about the relative power of ashe and vayne, because we're introducing another variable that is skewing results heavily. if we switch the supports so that now ashe is with morg and vayne is with thresh, then suddenly ashe is coming out on top!
but that's totally meaningless, because not only is every matchup different, but every team is different, and every player is different. but the key here is that any outside circumstance that can favor vayne could also favor ashe. "but what if the ashe player is teamed with bronzes, or what if she has a mordekaiser support, or what if she spontaneously bursts into flames at 5 minutes?" none of that actually matters, because any of those things are equally likely to happen to the vayne player.
there is a discussion to be had about how different AD carries synergize with different supports or deal with certain enemy supports, and it does pertain to whether ashe is balanced or not, but i'm not interested in even giving an opinion on that conversation. yes, ashe might be weak right now or she might not, but i have no idea and i dont intend to make any claims on that front. i simply offered an analysis of potential carry burst damage at level 1, 'on-paper'.
i'd also like to invite you to take a look at varus's wiki page here: http://leagueoflegends.wikia.com/wiki/Varus
his ult has no AD scaling, and is very different from ashe's because ashe's ult has unlimited range. global anything is powerful, cc even more so. to dismiss that offhand as somehow not significant is just silly.