From my experience of mostly being a Sona player... any time he nips out to grab a chime or two I get to go unload a full AA+Q+AA on their ADC almost for free. Which is anywhere from a third to half of their HP in lane. Which of course requires Shrine heals to fix, which requires he either back or roam for more MP... which leads to me again, well you know.
Oh and, you're going to absolutely require jungler assistance versus something like Sona + Cait. Otherwise the moment you leave lane your ADC is going to get absolutely mauled (Cait dropping traps on your shrines is fun). Nami is also another bad one for Bard, and is my go-to pick for when Sona isn't available or isn't the best choice. Basically, sustain lanes with better poke are going to give you a hard time.
As for what works with Bard? You preferably want somebody with at least a dash to make dives a harder proposition and a semi-reasonable way to get ranged farm. Cait, Corki, Lucian, and Graves work well. Vayne is a very bad match, both you and her require scaling to become relevant and because of that you are likely to not make it out of lane phase intact. Kalista is something of a special case, you really can't afford to roam until she's gotten her first major item and T2 boots and thus gotten her power spike from her mobility passive. And then we get to Ez... sigh I swear he makes a better mid than ADC. You get a good one, you are probably fine roaming the moment he hits six. If you get a bad one? Your lane is probably "done" at champ select.