So to open, I love playing Bard. I main support, and while I love blocking skilshots with Braum, going ham with Leona, or bananakilling with Soraka, the joy I get from floating around and collecting chimes is beyond compare.
Now down to the nitty gritty.
His passive is lackluster. I use it primarily as a way to sustain my mana. The chimes grant very little experience, and the meeps don't do that much unless the game lasts 50+ minutes, and by that time you are either stuck homeguarding to save your base or your team is bomb rushing theirs and need you for the team fights. They add to his damage and utility, but definitely not enough to make it worthwhile. While a farmed Nasus/Viegar/Sion/Thresh is a force to be reckoned with, Bard's passive scales surprisingly poorly into late game.
His q is also a bit weak. It travels slowly. Considering it is his only source of damage it has a rather low base Damage and AP Ratio (215 + 50%AP at level 5, Compare to Zileans bombs, which have an equally conditional and potentially more powerful stun yet deals 300+80%AP).
These facts and the low ranges, along with his innate squishiness make him rather terrible at the poke fest that dominates bot lane.
His heal? Once again, low AP Ratios. Fully charged it heals 230+45% AP, compared to Soraka's heal which is 240+60%AP, or Nami's which is up to a two person 185+30% AP, healing in total 370 + 60% AP, yet also damages enemies and provides a similar speed buff. Still it has its merits as it is the only remote healing spell in the game. Bard makes for an incredible leash. Placing three shrines before recalling allows the jungler make it through their first buff with full health if done properly. Yet because the AP Ratios are so low, and the flat 100 mana cost is so devastating early, Bard is not able to really shine as a sustain champion either.
Onto his E. Really the most appealing part of his kit besides the ult, his E is very situational, and the fact that it is open to both teams makes it really dangerous to use, and as a Bard player I am terrified to use it for fear that I'll mess it up. It is too easy to waste it as well. Too many times I have tried to get the long portal from dragon pit to tri bush, only to get the portal from the outside of the pit to the inside. If you are using it with plenty of time to cast it is wonderful, but it does not favor quick reactionary casting.
His ult? Once gain, something that most Bard players either are too terrified to use or too callous with. It is slow moving, once again, and thus hard to land. I place it on par with Janna's ult, except having even more potential, with that potential being in either direction, as a game changer or a game thrower.
Really, my biggest problem is that he is going to be impossible to use at any level below platinum, or even challenger. He is so demanding of the player and the team. His ult and e require coordination with all players involved, which most solo ques and even ranked teams lack. Unless you are playing with voice chat, you are going to have a hard time with it. Yes, there will be moments where he shines, but in general he is going to be considered trash until people learn to play around him. He changes the entire feel of the game, and he requires the same awareness of him that one would have to have when fighting an enemy blitz. He has the potential to affect the outcome of a game more than any single other champion that I can think of. In that regard he is extremely unique, and that is why I love playing as him, but I feel like there needs to be some payoff. He is excellent at roaming, but mediocre at poke and sustain.