I've been toying with the idea of making a kineticist for a bit, now. The class is quite flavorful, with some interesting options and a nice set of utility.

…That said, its core sucks.

Like, really sucks.

While it has a nice group of stuff to do, most of its abilities are locked behind Burn costs. Burn, on itself, is a conceptually interesting idea: you cause some damage to yourself in exchange to do bigger, greater stuff. However, the amount of damage the kineticist takes is, honestly, ridiculous:

At 1st level, a kineticist can overexert herself to channel more power
than normal, pushing past the limit of what is safe for her body by
accepting burn. Some of her wild talents allow her to accept burn in
exchange for a greater effect, while others require her to accept a
certain amount of burn to use that talent at all. For each point of
burn she accepts, a kineticist takes 1 point of nonlethal damage per
character level.

and

A kineticist can’t choose to accept burn if it would put her total
number of points of burn higher than 3 + her Constitution modifier
(though she can be forced to accept more burn from a source outside
her control).

Emphasis mine.

This mechanic makes it so that the Kineticist can't really contribute that often in meaningful ways in combat by doing the coolest thing in her kit – blasting – without getting herself really close to dropping unconscious at the first lucky attack that manages to land. Plus, even if the Kineticist has a hefty HP pool and can handle all that damage without issues, the number of Burn points it can take is limited by that other clause (3 + Cons mod), which further hinders its usefulness.

So, I decided to do some changes – the fewer the better – to it, in hopes of pushing it to the goldylocks Tier 3. So far, those are the changes I'm thinking in doing:

Take away the "per level" clause.

For each point of burn she accepts, a kineticist takes 1 point of nonlethal damage per character level.

Burn was theoretically a mechanic introduced to keep the kineticist in check and preventing it from going overboard. This class, however, isn't that strong to begin with, so I think that 'nerfing' Burn won't make it too overpowered.

Secondly, just remove the entire con-based limitation.

A kineticist can’t choose to accept burn if it would put her total
number of points of burn higher than 3 + her Constitution modifier
(though she can be forced to accept more burn from a source outside
her control)

This limitation makes no sense. Other classes can use their options several times per day, or have several different options to pick from. The Kineticist has a single pool of resource as it is, and it is far too limited to provide good gameplay. This needs to go.

Third, change how Gather Power works. Instead of offering a discount of Burn costs…

Gathering power in this way allows the kineticist to reduce the total
burn cost of a blast wild talent she uses in the same round by 1
point. The kineticist can instead gather power for 1 full round in
order to reduce the total burn cost of a blast wild talent used on her
next turn by 2 points (to a minimum of 0 points). If she does so, she
can also gather power as a move action during her next turn to reduce
the burn cost by a total of 3 points.

…Make it so that Gather Power gives the Kineticist a nice (and much needed) damage buff:

Gathering Power in this way makes the Kineticist Empowered for a number of rounds equal 3 + its Con modifier. While Empowered, the Kineticist's adds +1 damage to the damage of her Kinetic Blast, plus +1 for every 2 levels above beyond the 1st. The kineticist can instead gather power for 1 full round in order to increase the damage of her kinetic blast by 1d6, plus +1d6 for every 2 levels beyond the first.

I'm also thinking in bumping the Kineticist skills to 6 + int per level and giving it more or less the same class skill list the Magus has, but I'm not sure if this is needed.

Are these changes reasonable? Are they enough to push the Kineticist to Tier 3?

A few years down the line, I've found the class that essentially made the Kineticist completely obsolete. If someone else is having issues with a kineticist build and wants to try something with a similar flavor but way more interesting, I can't recommend the Elementalist (from Spheres of Power) enough.