As said above me, I don't think that Boss Hint is inherently unbalanced, although not telling you about the Garden that can save your team or where it is at is a really cheap move, the primary issues with it is that the players need to select proper character classes to play and have a balanced team and then work together as a team. Voice chat has probably never been more vital to success in GW2 as it is in this game mode.
The teams I played on generally didn't have a problem clearing the Healing Burgers or finding the Garden to spawn if they had played through already and had figured out the bit about the Garden.
Skilled players could generally pick the right characters to play and could stay alive long enough to be healed and people working as a team would normally be moving as a group or in twos so getting revived wasn't usually a problem.
Getting to the end is completely possible, besides the bit about finding and growing the Garden when you eliminate the Burgers, the hardest part right now is getting the players coordinated so that we have the biggest chance of success.
And for the record, the Vampire Sunflower is your best choice since she can self heal without worrying about dropping a Heal Flower.
