Bard does have CC and ranged harass. You do know that, right? Bard players need to start using a checklist on whether or not they should leave the lane to roam.
1) Is the ADC returning to base when I don't need to? Then Roam.
2) Is the enemy low enough that engaging 2v1 will likely get one of them killed? Roam.
3) Is our jungler nearby and has he shown the map awareness to respond to action close to his position? You can roam.
4) Is the enemy incapable of towerdiving effectively and they are pushing up? Roam a little.
5) Do you have your ult and are you pretty good at landing it from a distance? Sure, roam to max range because you can still protect your ADC from there in a pinch.
Basically, you should ALWAYS be asking yourself before you right click to the nearest bell, "Will my ADC be relatively safe from everything except his own stupidity?" If they can tower dive him, you don't leave. If they can easily chase him down, you don't leave. Too often I've seen Bard leave at the worst times and stay at the worst times. Guess what? You're Bard. If you are alone and they are pushing, you aren't going to save the tower. You don't have waveclear. You are probably better off using that opportunity to roam, and then you return to the lane when your marksman does.
That's not to say ADC's with Bard as a support don't act stupid sometimes. They do, but far more often, I see the Bard misplaying the situation and getting the ADC killed than I do the ADC TRYING to engage and fight outnumbered.