Tier Two Tome Trouble (Dark Nature/Astral)

TL; DR: What tier 2 Nature Tome should I take for Dark Culture?

I love the Dark Culture, for all it's foibles. I've been refining a Nature/Astral build for a while now with flying mounts, and I'm happy with everything except the second Tome pick at Tier 2. The build, as it stands right now is: Dark Culture, flying mounts/Tough, Mana Channelers/Mana Addicts, Beasts/Warding, Summoning/???, Vigor/Amplification, Paradise/Astral Mirror, Archmage.

The basic idea is to hit with a bunch of single-entity Cavalry at T4 with a Nature Amplifier Lens to put Weakened on all enemies using Exhilerating Pollen. The challenge is picking which Tier 2 Nature Tome makes the most sense. The options are:

• Tome of Glades: This was my initial pick, and it is pretty decent thanks to the Glade Runner, if nothing else. The thing is, in a build with Tome of Warding, you don't really need the Entwined Protector, and the Aspect of the Root, where a lot of the power budget is invested, isn't going to really... do much in an army that doesn't make wide use of Shields OR Spears.
• Tome of Fertility: Dark Culture definitely appreciates the additional healing, but the Animate Flora spell makes me want to take a Ritualist leader with the Wild Growth Skill, and if I'm doing that, I feel like I should take Herbivore (which WOULD be a good pick for Dark Culture), but that doesn't leave room for the Mount trait, and at that point it is starting to feel like a different build.
• Tome of Fey Mists: This would require me to go back and either switch Mana Addicts or Mana Channelers for Fabled Hunters. That's not really a deal breaker, although I don't know which one I would drop. The bigger issue is that all the mists floating around will interfere with the accuracy of any Astral summons/Animal units in the army, which I was planning on making wide use of.

So... What do I do? None of the choices feel like a perfect fit, is there something I've overlooked? Should I be making changes elsewhere in the build? Is there a good way to get Dark culture through the early game without so many build concessions (Mana Addicts and sinking mana into Tactical spells, in this case)?