I am actually curious - why do people like Assassin Vine? I feel like Treant is a pretty clear choice, because Treebeard was an awesome character in LotR. Shambling Mounds = Swamp Thing, and he's pretty awesome post Alan Moore.
Maybe GMs like using Assassin vines in their adventures? But that's the only reason I can see voting for it. Not really understanding the love for it...