I don't think it's that bad. Once marth's % get above 50/60% (and it's pretty easy to get there) it becomes easier to just push him away, and he has approach yet again. Don't try to camp from far away with only arrows, since he can dismiss these quite easily.
You need to stay just outside of his range, and annoy him with arrows to make him react to them. Punish rising aerials with your own, empty short hops with arrows or fair. yeah obviously you'll need to mindgame the fact that it'll be an empty short-hop... however if you are, like you should be, out of his immediate range, you should be able to get your fair started before he can actually interrupt you. Don't count on this too much, cause the main point in this match-up is to MIX IT UP heavily.
We get juggled pretty hard; don't hesitate and go for the ledge if you have to.
Finally, don't lose any opportunity and punish everything you can (if you mess up or don't know what you can actually punish, you're gonna get DB'd or DS'd all day) . Edgeguard him like there's no tomorrow, juggle and punish his airdodges if you get a throw or usmash/tilt in.
Don't rush for the kill. It can come in the form of an edgeguard (invincibair, arrow gimps, regrab the ledge with WoI if he thinks you're going for a bair), a well-spaced ftilt+arrows, an Fsmash (i never kill with this lol)/Dsmash or if you're desesperate, hyphen smash.
The only way you're gonna land a bair is by trading with his fair (it happens...) or as a punisher on rising aerials or whiffed UpB.
well I might be wrong on some of these, but that's how I see it.