Earth/Storm IO advice?

Lightning Storm is a pet, so the proc will only have a chance to go off when you cast the storm. Because it is a pet, none of the strikes will benefit you.

I like the Devastation Chance for Hold in Lightning Storm if you have the slot for it.

Far more important is slotting up Freezing Rain for procs. I generally have 2 Recharge and the procs in Achilles Heel, Posi Blast, Lady Gray, Impeded Swiftness. None of those are overly expensive.

Impeded Swiftness can also go in Quicksand (which I use a lot) and in Snow Storm (may not be worth it unless you use it a lot).

Procs work really well in Volcanic Gasses due to the odd way it works, but there are so many good procs for that power that it is tempting to give up some of the good slotting in it; Unbreakable Constraint, Ghost Widow, Neuronic Shutdown and even Lockdown for stacking mag all work, plus Posi Blast and Will of the Controller will all go in this power, but you want some Recharge and Hold in it, too. Don't bother with the Baz Gaze proc.

Stone Cages can take Grav Anchor Chance for Hold (great), Posi Blast, Trap of the Hunter and Will of the Controller. I use 5 Grav Anchor and the Posi Blast proc.

Earthquake can take Achilles Heel and Lady Gray, Explosive Strike and Force Feedback. I went with Achilles.

Animate Stone: If possible, put BOTH +10% Resistance procs (Expediant Reinforcement and Sovereign Right) as that added resistance really helps Rocky's survival.

Tornado: Absolutely get that new Overwhelming Force KB-to-KD proc.

I figured since earth control has -knockback in it's aoe immo I'd be okay.

Stone Cages has a 20% accuracy penalty. Even with a bunch of accuracy slotted and some global accuracy, it still misses. Tornado tends to skip around a lot between targets, so if any foes were missed, 'Nado is likely to find them. Plus, the Tornado often runs around in a wider area than your cages. The proc provides a bigger benefit to Ill/Storm, Mind/Storm, Grav/Storm and Elec/Storm who don't have the -knockback AoE Immob, but it still helps with other combos. It is not essential if you really need that slot for something else -- but I really like it.

And even the basic benefit of being able to just use Tornado regularly without having to babysit it is very useful. Or use it in two different places if you have enough recharge without any worry.

Also spamming AoE immoblizes for the -KB tends to burn alot of endurance without a sizable amount of end recovery/reduction. And you end up having to spam it because of the above accuracy penalty, to make sure that the entire mob is hit.