wow, i cannot believe i didn't know that this thread existed
I'm still on the fence with Lilligant tbh. The fact that it requires setup to deal with some of the more common types (Poison and Steel ala Team Plasma) really cuts it down, no matter how easy the setup may be. It'd go straight to High if it had some form of coverage move, but as it stands, Mono-Grass just doesn't cut it for me. I won't cast a vote, but those are my two cents on Lilligant.
I'm using a Lilligant on Challenge Mode White 2 (that is, not even the trade), and it is brilliance, so I'll make the case here for it.
Setting up Quiver Dance on this thing is so easy, it's stupid. Lilligant's fast enough that you can Sleep Powder them immediately, and two or three QDs is generally all it takes to start ripping massive holes in basically everything, since after two QDs double SpA pretty much balances out half base power. Is it -ideal- against Poisons? No, it's not, but expecting it take them on reasonably is like expecting Conkeldurr to take on Psychics, or expecting Braviary to fight Rocks and Steels. Half of the Frigate is other things anyway (Krokoroks, Scraftys, Raticates, Watchogs, Liepards, to name a few), which Lilligant handles quite well anyway. It's not Lilligant's shining moment by any means, but tell that to Magnemite when it's in Driftveil City.
The point of QD is for the bosses. You don't need it for the mooks, they already die to Giga Drain/Petal Dance. Just throw Sleep Powder at something, set up on it, and go to town. Clay, for all his Excadrill, is swept. Even Skyla's Skarmory is set-up bait (well, on Normal Mode, anyway). Marlon is a joke. Colress can't do much to you, outside of Klinklang and Magnezone's Explosion, but Magneton is set-up bait and you should have Sleep Powder. Ghetsis's Cofagrigus is set-up bait (though that would mean having to fight Kyurem with Lilli). So are Shauntal's Cofagrigus and Caitlin's Musharna.
Lilligant stands tall and proud amongst the greats, even without a coverage move. Wherever there are weak special attacks being thrown around, she can Quiver Dance. Wherever Pokemon lack Insomnia, she can Quiver Dance. Wherever the AI can't phaze you, she can Quiver Dance.
Leech Seed is also cool.
Also, are the write-ups in the OP set in stone? Just skimming them, I'm seeing some questionable claims (Shadow Ball is good on Metagross, Roselia can't evolve until Opelucid), and some of the tierings look like they're more theorymon than practicemon (having used Conkeldurr, I would not rate it Top, that's fishizzle). For that matter, there doesn't appear to be any standard for what constitutes certain availability ratings; for example, Route 4 is labelled as everything from Early to Mid-Early to Midgame.