Although I'm enjoying my Occultist Vortex, I do want to try a CoC based build. I don't want to play cyclone. Is Power Siphon/Barrage a good enough trigger for it? What spells would be linked to it? I tried looking around in the guides and didn't see anything pop out, I haven't played a CoC character in a couple of years probably.
I like power siphon, but it's best for easy clearing, but really ramps up on multiple targets. Barrage is really good single target and should be good enough clearing if you have the right skills. Also the bows you can make for barrage CoC are very good. Double damage, elemental damage, +to gem levels, good crit base, etc. Wands have really high base crit as well and can get pretty good stuff (spell crit, multi, spell flat) that can be paired with a nice shield for damage and defenses. Spectral throw would also allow you to use any weapons you want or a shaper 2hander with CoC built in for a 7 link essentially.
For spells it depends. Arc is basically a must. The damage is insane and the clearly is amazing. Ball Lightning is also pretty awesome, but it really needs slower projectiles somehow (works with spectral throw setup) to really shine. If you're doing barrage or power siphon you'll want to be ranged so remember that CoC procs from the CASTER'S position. So stuff like glacial cascade can be really good, but it comes from your feet when you proc it so if you're not close enough it's not hitting. That's why projectiles or large area (bladefall, firestorm) are the way to go. Some people used to use ethereal knives back in the day too, but I don't have any experience with that.
In order of "best' for a ranged CoC build I'd say:
Arc
Ball Lightning
Ice spear/Freezing Pulse
Bladefall/Firestorm
Fireball/Frostbolt (doesn't do much damage unfortunately, but like Freezing pulse has a very good threshold jewel)
When I made my CoC build I tried to look up info, but really no one had done pure CoC builds (not including mjolnir/cospris type stuff) since like 2.6. I think people are still figuring it out. Pretty much only thing I can say is Arc is top dog by far.
I made a new build last night. I did a cheapo PP build with double 5link and 6 link wands (shaper/elder) which I put Ice Nova and Vortex in respectively. Then I put "cast triggered spells on skill use" enchants on it. Then in my armor I just have a frostbolt garbo cast I spam to proc those two out of the frostbolts. Ice nova only procs once, but I can get 5 vortexes out pretty regularly. I had to get some cooldown recovery because innate skill trigger is 4seconds, but I got some on boots (13% iirc) and you can get 10 on belts with craft or 15 with one of the elder ones (or shaper I don't remember). So looking at 30% CDR on a 4 second cooldown puts it at 3ish seconds. Not bad. Not nearly as good as PP but they're an exalt each. My wands were 5c and 20c, but effectively I'm running a 5 link, 6 link, and 5link.
I was originally going to do frostbolt on cast while channeling winter orb, but as I learned at lvl 68 CoChannel only procs triggered spells at the start of the channel. Not throughout. Made me pretty sad, but really freed up my chest for a good ES robe with just 4-5 links (I'm CI Occultist of course). So far it's not bad and when I actually get my gems to 20 and stack crit multi I should really destroy shit.