(TLDR: Take Extra Focus Power (Telekinetic Mastery) as your 9th level feat. Swap out Lead Blades for another spell, I recommend Liberating Command.)
I'd say take Extra Mental Focus more than once if allowed (though RAW you can only take it once).
I think Extra Focus Power is pretty much always useful. Personally I'm a fan of Telekinetic Mastery (Transmuatation) at level 9. It's the equivalent of a 5th level spell and you're getting it 4 levels before you have 5th level spells. It can be a damage spell, a control spell or even an out-of-combat utility spell. Also, as a Focus Power it only costs 1 Mental Focus per use, which means you can spam it more than even a Wizard of your level if needed.
One note on your character: I see a lot of Occultist builds stacking Enlarge Person with Lead blades to get bonus damage, and I honestly don't think it's worth it. This would take your Nodachi from 1d10 (~5.5) damage to 2d8 (~9) damage, to 3d8 (~13.5) damage. That's pretty good (~+8 damage), but it's costing you 2 rounds of buffing, and presumably you're taking a 3rd round for Legacy Weapon to apply (whatever)-Bane to your weapon for +3 to hit and ~+10 damage as well. Taking 3 rounds to buff, your weapon probably isn't worth it. Even if it does work out mathematically - or you have time to prebuff so you're not wasting rounds - do you really need to gove yourself +18 damage before you start fighting? You'd probably do fine with just Legacy Weapon, so adding more damage buffing spells means you can't take more utility/defence/whatever spells (eg. Over-specialization might not be as good as diversification). I would keep Enlarge person (because it adds battlefield control as well as damage) but swap out Lead Blades for something else. My Occultist has Liberating Command as a 1st level Transmutation spell and it's saved party members enough times to be 1000% worth it.
Other than that, looks like a strong, flavourful character =)
