Bard Ability Review
Yea sure he can be a troll with the portals and the ult, but a lot of other champs were considered trolls too. I mean anyone can assist the enemy team, not just specific champions.
Q- Slow is a good tool for disengage, and probably a stun because the marksman and the jungler are most likely coming toward you in a straight line. You can also stun by hitting an enemy and a wall btw.
W- You could put a lot of health pads hidden on a brush so assassins will try to kill a low HP champ, but then the fully powered health pads will heal the ally and then with the extra HP from other health pads your ally can kill the assassin.
E- You could use the portals to bait assassins to you, they don't know that your whole team is hiding on a brush waiting to pounce them. They can't escape or have to burn a flash because the portals are only one way portals. You should follow up with the q and hit a wall with it to stun the assassin before they can flash.
R- You could use your ult to tower dive the enemy team. Secure a dragon or baron because it stuns everyone including baron and dragon. Follow up with a portal to go and kill the baron or dragon and use q when the enemies are targettable to stun 2 enemies, which should be the burst champions like mages and assassins.