I'm not a big fan of a druid, but I've tried him several times. Per my view, your book lack couple of things. This is just my personal opinion based on the games I've had.
1) For a person that relies on a strategy with growing a lot of plants and luring enemies into your "Garden of Death" your mage is too defenseless. You have only Barkskin and Rhino Hide to save you from attacks. What will you do if you get teleported into 2-3 big hitters, like Steelclaw? Do you rely on Nullifies and Blocks for this case?
2) You don't have what I call "A Big Threat". Let's say you start growing your plants, you'll need about 3-5 turns to set it all up. During this time another mage can summon several of his creatures, some of then might even be ranged. As soon as he does it, there is no point for him to run into your zone and attack, he will just shoot from the distance, as your walls don't block LoS. "A Big Threat" is something that makes him want to move to your part of the table or react to it.
Example can be:
- Steelclaw with several enchantments running to your mage
- Grimson Deadeye shooting at you every turn
- Idol of Pestilence of Altar of Sculls
- Wizards tower with some dangerous spell attached.
All of the mentioned make the enemy mage react and try to deal with them as soon as possible, thus making your set up easier.
3) Warlock is going to be a big pain for you. Fire just literally kills druid's garden.
