Fell
This is why by contrast to many in this thread I really don't think bard needs anything nearly as spammable or unconditional as monk FD.
But I do think the need something to keep a random bad diceroll from becoming a 6-8 pull that they have no way to prevent. No matter how you dice it a class that runs that risk is not going to be a serious consideration for puller in hard content.
A minute plus cooldown aggro drop would be more than sufficient even if it had other downsides such as a cast time or no mechanism to keep nearby enemies from immediately reaggroing(so it only worked if you use it before enemies close).
Bard doesn't need any more ability to split or single pull I'd agree- those are strengths are the specialties of other pullers(monk/SK) and bard definitely shouldn't be flopping often enough to split with. What bard and any class meant to be a puller does need is something to allow situational awareness and a prompt response to recover the occassional catastrophic lull or similar ability crit fail from pulling everything in the room.
An aggro drop or memblur is the simplest way to make this happen, but stronger, faster, or AoE emergency CC would do it too.
CC should of course be important but I also don't think a bard should need a pocket enchanter backing them up to take on the role of puller in challenging endgame content.