I have Played my Occultist from playtest to just this weekend at a Con. He is level 7 and I've had him on slow progression for 80% of his games. He is Necromancy Transmutation Focused. Skeletons and Buffs. During this time I have come to a few conclusions about the Occultist Class.
One thing is the Mental Focus and Number of Implements starting even when we pick up our 3rd implement becomes strained. Yes Divination has some awesome resonances but so does Transmutation, Abjuration, Evocation, and Enchantment. So when you get another implement at 6th It starts to become difficult to Spread them out evenly and meet the prereqs for the Resonances, not to mention Focus Powers. So a bit of actual focus is required. Will you be Combat? Pick up Transmutation and the battle Host Archetype. You will hurt for spell Schools but you wont have to worry about mental Focus Distribution between you're AWESOME Transmutation Resonance, and other Implement Schools. Just Pick Up Abjuration, Conjuration or Necromancy. Whatever catches your fancy really, extra protection, teleporting, or flanking buddies respectively. Heck get Divination to help See the enemy, while the fighter stumbles in the dark, or fails to see the Invisible caster making him punch him self.
Yes You could pick up Extra Mental Focus, Max out your INT and/or get a Headband of INT. But you will likely ALWAYS suffer from "lack" of Points if you just go Pure Occultist. Or dont take a Implement/School Twice.
I Love this Class, If made/played correctly you'll be hard pressed to not find something different to do in and out of Combat every session. While I have no Campaign experience with them. I can hardly Imagine them faring any worse in any Adventure path, home campaign, or the like.
