2 words, forced riposte. :)
But yes, if you don't have that hypnotic suggestion then killing them quickly is your only good option. Having everyone use AoE moves to get through the dodge tokens is a good way, other options includes the maid's (enhanced) feather duster or the mage's magic missile.
They also lose the dodge tokens when they grow, focusing on one of them as soon as it does is a good idea.
Encounters against the small Vines are ok, but if you're fighting multiple Alarune Horticulturalists with other opponents they can stack up Vines in the Reinforcement queue, which looking back probably just needs good target priority.
There is a 4 Clustered Vines encounter however, and the turn queue at the top had 20 slots due to the multi hit attacks. It is an ELITE encounter though, so I'm not shaking in my boots at this one, but yeah I am definitely not fighting that again.
