My friend and I whipped up a couple level 10 occult classes each to try out a couple combats. We picked random combats at CR10 and CR12. The CR10 was a young green dragon and a stone giant. The CR12 was 3 bulettes and 3 chimeras. We generally did very well in both combats. Only the breath weapons and the bulette pounces did much damage. Now for more specific thoughts and feedback per class.
Geokineticist: My friend built him to be a melee kineticist tank using kinetic blade/whip with weapon finesse (his interpretation was that the whip was finessable since it functions like blade which included light weapons). He also had the Pushing substance infusion, but the monsters we were up against were very hard to bull rush. He proved to be our highest damage dealer (other than save or sucks) and was VERY tanky with 7 dr/adamantine (2 burn for 2 extra dr). He also had the water defense for the shield to boost his ac even higher (he was sitting at 31). He would use Ride the Blast to get into melee then stay there using move actions to avoid the burn to pull out the whip. He had combat reflexes to make use of the whip AoO's (of which there was only one, but it landed!). The concentration checks to use melee blast options seems like a completely unnecessary penalty. Additionally, he thinks that when using the melee blast options, that kineticists should be able to make all of their iterative attacks when full-attacking (he was using move actions to avoid burn, so it was moot in these fights). His blasts were averaging around 25ish damage per round as long as he made his concentration checks. He did not have combat casting, but he did have a +2 to concentration trait.
Occultist: My friend built him with Abjuration (cloak), Conjuration (compass because there are no summon spells), Illusion (ring), Evocation (wand...of CLW, lol), and Transmutation (belt and weapon). He put 6 of his mental points in his belt for +4 dex, 3 into his weapon for the shocking property, 6 into his wand for blasts (ended up not using them), and 4 in his compass for heals and teleports (2 used on healing). He was built as an archer with some support spells and a few blast options through his implement. He functioned reasonably well as an archer and was able to keep up reasonably well with the Geo's dpr. Once things got a bit hairy in the second fight, he used Greater Invisibility and dropped into a healing role while the Geo tanked up the bulettes full attacks. My friend really liked how the occultist played, but he did not like that spending points from his implements reduced the resonant powers which made him very reluctant to spend them.
Mesmerist: I felt like the Mesmerist is pretty railroaded on options. The tricks were neat but need some work. I was able to use my Mirror image trick to good effect. If you are looking for single target control, this is where it is found. It does need the Stare ability to be greatly buffed. I feel like this should be more of a core feature of the class.
Psychic: I feel like the Psychic has great potential. With some expanded Disciplines and a little work on the amplifications they could be pretty cool. I think the Disciplines need a kick in the pants a bit. I played the Discipline of Abomination- This has great flavor. The few measly rounds per day that you can be your Dark Half was very cool, but the amount of time you can stay in that form needs to be greatly increased. I like some of the Psychic spells, although I feel that Psychic Crush is a bit over powered against low will targets. It is a complete save or suck spell that ruins fights at mid levels and up. I also feel like mind thrust is a good spell despite it's low damage potential compared to other spells. Also I do not see the need for all of the spells to have so many versions. Why not just have the base spell scale with level like most spells? Overly complicated in my opinion. With only a few single target blasts and some control spells I feel the spell list or Disciplines needs a lot of work here.