The trees are a great solo/pvp oh @#$%& button.
When you have three mobs on you, attack one, and pop the trees on the other 2.
While you are attacking one mob, the other 2 will be attacking you trees-giving you some time to kill your mob, heal and then take on the other 2.
The trees also hit pretty hard and will usually bring one of the mobs down to 20% health if not kill it. So you go from a 3 on 1 situation to a one on one fight.
In pvp, they are great to pop on a caster, or to beat on the rogue who just jumped you. Its great fun to drop them on an unspecting player and have the time to wind up a starfire before they figure out what happened :)
As far as raiding/instances i only really use them on aoe pulls and maybe at the start of a boss fight, so if your looking at hardcore raiding, you can probaly skip em, but its only one point so i say it's well worth it.