Credit to Resto Druid Trick: Tree of Life forever (WoW PvP/Gameplay) By Nequimwow - World of Warcraft Movies
Right after you accept the arena you hit your tree of life before you get ported. You basically have to spam it. You gain all of the benefits of tree of life (instant roots, instant regrowth, increased healing, lifebloom on multiple targets) and even more. With the lifebloom swap glyph, once you get 3xstack of lifebloom on a target, just putting 1 lifebloom on another target automatically makes it 3x stacks. So you can easily keep 3 stacks lifeblooms on everyone.
Once you are in the arena shifting will make the buff disappear, but if you do shift the cooldown on tree is reset so you can pop tree for 30 seconds more as normal.
I did have this happen to me mid arena once before but I could not recreate it, I'm sure it's possible.
I'm sure this will be fixed very soon.