It is the second day, give Bards a break. There are bound to be mistakes, and his purpose in teamfights hasn't really been identified yet.
My general plan for teamfights is thus.
Place a few Snowflakes (W) back by your ADC.
If the enemy team is separated / out of position, ult half of them, preferably the tanky half.
If not, use E to reposition and try to land a double stun q. If you can hit that, you are golden.
Use E and or the Snowflake speed buff to escape if the fight goes awry.
If someone chases through e, q them just as they leave, pinning them to the wall.
From what I see, what he does in team fights is dictated by the team comp. A hard engage / Dive the carry team means he has to land his ult on the enemy front line and only the enemy front line. A protect the carry team means q'ing anything that gets past his front line and ulting them if necessary. A poke comp means snowflakes are the focus, and stunning anyone that dives at them with his q.