Having actually tried Bard as a jungler in the PBE I can safely say he is not a viable pick. You do nearly no damage. Bard has possibly the worst scaling I have ever seen on a champion. If you dont believe me when he comes out just try to go full ap with him. Its actually a joke. His Q must scale off of like 0.25 of his ap or something. Also hes unbearably squishy and as I just said he has no damage so no real kill pressure either.
He can barely even survive the first camp with a two man leash. Meaning you will have to back after two camps at most. You will honestly just end up spending most of your time wandering around collecting chimes but since his ap scaling is so bad even with a ton of ap you still need over 100 chimes for your empowered AA's to even do damage. His W is nice for sustain but it doesnt help much consider how long his clear times are.
You pretty much are forced into going Rod of Ages to even have a hope of clearing camps and living and since Bard already takes forever to properly start scaling you end up even more crippled until like 30 minutes into the game. His ult is good for ganking but its an extremely slow aoe skill shot thats hard to land since most enemies can just lol walk out of it before it lands plus it can hit your teammate if they decide to be stupid.
Its just not worth trying. Do to all of the above things all of the current meta top junglers will laugh their way into your jungle and kill you with one auto attack due to how low you will be in health and then gank mid and snowball their mid lane. It simply does not work.