I was so saddened by the lack of answers that I gave up and forgot to check in at a later time :) so, please excuse my late reply.
First, thanks for the "create primal event" tip, it is a good reference point. I somehow managed not to come across that one during my research of the subject.
I'm not sure about randomizing the range and direction too, on top of the random effect. The random effect is already random enough, could help you, could hurt you, or it could be just something weird or interesting that neither hurts nor helps. Which is fine for the most part, to make things more interesting and unpredictable, to create new unusual situations for the characters to react to, etc. But, if the effect is too random, or turns out to be hurtful more often than helpful, then the characters will simply never use it again. I mean, if a character is supposed to keep using something, then that something has to be beneficial in some way, at least over a longer period - why would anyone want to shoot themselves in the foot repeatedly?
Keep in mind that this is not a talent that you can simply pick at level up. You have to put effort into obtaining it (I'd say a lot of effort, but I guess that depends), and as such, you'd want to be able to use it to help yourself, not hurt yourself. If its goint to hurt you more than help you, then why bother putting in all that effort in the first place?
Therefore, a character would most likely want a little bit more control over the primal magic, not less. When deciding to trigger a primal event, its bad enough not knowing if it might cause an explosion or a buff, but then also not knowing in what direction and how far? That's too much randomness for it to be worth it. The chances of something helpful happening would be far too low. For example (and I'm making these numbers up), lets say that normally, there's a 33% chance of something good happening, a 33% chance of something bad happening, and a 33% chance of something neither good nor bad happening.
Then, if we randomize range and direction too, there will be a lot of situations where the good and bad effects happen too far away and/or in the wrong direction for them to have any effect on the characters/enemies. Meaning that they would now fall into the "neither good nor bad" category. So for example, there'd be a 10% chance of something good happening (in the proper place), a 10% chance of something bad happening (in the proper place, and an 80% chance of things that are neither good nor bad happening (or things that dont have a meaningful effect on the combat or whatever situation the characters are in). So in the end, you're wasting your action on something that only has a 10% chance of doing something good, a staggering 80% chance of basically doing nothing, and a 10% chance of doing something bad. Again, the numbers are made up, I havent done the math, I'm just trying to say that the chance of "nothing happening" would be much greater than anything else and as such it would most likely be a waste of an action to use this talent.
Anyway, yeah the list is just a sample. There are plenty of other random effect lists on the internet though. I obviously havent gone through them to see if they all list the specific radiuses, durations, etc. It would be great if they did, because these change from effect to effect (they are dependent on the effect), but one thing that shouldnt change is the range of the talent itself (the range should be dependent on the talent). As in, the talent should provide a range at which it can be used, and then the effect should provide what happens there and for how long, etc.
I have also come to the conclusion that it's probably one of these 2 options:
1.) range 0 (centered on the kineticist), in which case the kineticist must either always be excluded from the effect, or have the ability to choose to be excluded from the effect (for instantaneous effects like an explosion going off. If the effect persists, then it should probably affect everyone in its radius. There are probably exceptions to this that I cant think of right now)
2.) range greater than 0, in which case if the radius turns out to be big enough to reach back to the kineticist, then the kineticist is a fair target for the effect.
What exactly should "greater than 0" be? I'm not sure. The simplest range would be 30ft for a base kineticist. Because surely if he is always able to manipulate strands of aether within 30ft with his blasts/other talents, then he can also manipulate them in a different way (into a primal event) at that same range, right?
And if he has taken Extended/Extreme Range, maybe allow him to increase the range.... if necessary, even by paying the burn required by these talents.
I'd personally lean more towards the 2nd option cause I really dont like it having centered on the kineticist. It complicates things about affecting the kineticist etc. And, since the kineticist probably doesnt want to get its allies caught in the radius, it kinda forces him to run ahead and jump into the middle of the enemy formation before using this talent, which can be very much problematic.
I guess I can share my experiences with it so far. It came up a whooping two times.
1st time was soon after I obtained it. Me and an ally were in a room with a minor boss, while 2 allies were outside the room. I triggered a primal event which turned out to work like Confusion on everyone in a small radius. The DM insisted that the effect is centered on me. Dont remember the details, not even if I had to save against it (this was many months ago), but I know that the ally and the boss had to save, and the ally failed, while the boss succeeded, causing serious problems for us.
I was very cautious with it since then, basically never using it again for a very long time in fear of causing something terrible, if using the talent while being close to allies (which I am, most of the time).
So the 2nd time was in a fight with more participants. We had like 7 NPCs on our side (but they were pretty weak), and the enemy force consisted of about 8 normal enemies and 3 stronger ones. The 8 normal enemies were all standing together on one side while the 3 stronger ones were coming in from the other side. One ally took off to meet the stronger ones head first, the other two allies moved a bit away from me, so I felt that if I move closer to the other 8 enemies, I might get to trigger a primal event without catching my allies in it. I did just that, and the effect that happened forced everyone in its radius to roll two d20s and take the worse result. The radius was pretty big too, but not enough to reach my allies. It did reach almost all enemies and the remaining NPCs (the NPCs were weak and basically died in 1 hit from the enemies). However, the primal magic caused everyone to miss a whole lot more. This ended messing up the enemies way more than us, they had a hard time hitting even the NPCs, which survived for much longer than they would otherwise. The NPCs didnt have much of a chance to hit anything to begin with, so this additional debuff didnt make them that much worse. And as for me: I also have an energy blast/blade, which targets touch AC, that is usually much lower than regular AC, giving me a good chance to hit the enemies even with the debuff. So, while my 3 allies were busy killing the 3 stronger enemies, me & the NPCs were keeping the rest of the enemies occupied, and I was slowly wearing them down with my energy blade. I'm sure that without the primal event, the enemies would have killed all the NPCs in 1-2 turns, then ganged up on me, and I'd have to run, or my allies would have to help out, making the fight much harder. Instead, the NPCs kept standing, I was even damaging the enemies, and when the allies have dealt with the other threats, they came to help finish off these guys too.
So the 1st time I used it, it turned out terrible and made me never want to use it again. The 2nd time I used it, it turned out pretty good, but still worried about using it unless I again get isolated from my team. The fact is, that even if circumstances have made the 2nd time go better than expected, its still true that the usefulness of this talent would be increased if it could be triggered from range, not centered on myself. As it is, I've used it twice in like a year of gaming, which is not nearly often enough for a talent that you have to work this hard to even obtain. If it had a range (even a short one), it'd get used more often, because a talent like this (that you have to work for) deserves to be used more often than that.