Pawlabear, your advice sounds correct for 7th edition, but I think it's out of date! 6 treekin make a Lot of sense now, although of course it really hurts to get hit with a cannonball (unless it sticks in the tree in the first rank- happened today

).
Musicians allow you to do a "fast reform", which is crucial now! Meaning you can reform and then move (but not march) normally.
I do agree that dryads are a steal!
As to the list, I like it but it feels small. I'm assuming you're going to stay as far back as possible, shoot and cast magic, and then charge in with the treekin / treeman when
th enemy gets close. It's a good plan, but will you be doing enough damage at range to make it work? Especially since lore of life seems to primarily be a "buff" lore, unless you get dwellers below? (Hopefully I'm not confusing lores, it's late!)
Also, what's the reasoning behind putting the caster in with the glade riders? It seems like that should Definitely be target #1 for your opponent, and they're fragile.
Nice list and I'd be interested to hear what tactics you have in mind for it