jonnyblais

I don't think you're a light armor caster:

• Given that Con is your key ability score, your HP is actually more like a Ranger or a Summoner's Eidolon, who would pretty commonly step into flanking and would be exposed to similar dangers (and you're better off than a Swashbuckler or a melee Rogue, and those are better off than most casters)
• Light armor where you hit the Dex cap is just as high as Medium armor where you hit the Dex cap, so again, you're more like a Ranger or a Summoner's Eidolon: middling in terms of AC (same as a Swashbuckler or melee Rogue and much better than casters that don't hit the Dex cap. Those casters that do meet the Dex cap sacrifice their Con, producing an even bigger gulf in HP)
• Casters don't have Water Impulse Junction, Air Impulse Junction with Mobility, or Lightning Dash to get away both without provoking reactions and without spending an entire action just to Step
• Casters don't have Winter Sleet's action tax for enemies outside of it approaching (Stride to aura's edge, then Balance over to you).
• Casters don't have Winter Sleet's Balance chance to spend actions and even turns: I looked at Archives of Nethys's creatures table for creatures without Fly and without Acrobatics: out of 2604 total creatures, 1065 have neither. An untrained Acrobatics check opens up a pretty darn good chance of a Failure at nearly all levels, in which their action is wasted and they do not actually move, or a Critical Failure, at which they fall and their turn ends. There's also the 5% chance of the 908 non-flyers who do have Acrobatics to Critically Fail into a Fail at a lot of levels, which is useful on a long enough scale just by itself.
• If a creature fails Balancing, it won't fall within flanking distance of you (unless it has Reach, but Aura Shaper will keep up with the Reach that enemies tend to get as you level). It will fall a square or more away from you (still within your Reach or Throwing Weapon range).

On the diagram: the enemy on the left can't Step. It has to Balance, forcing two possible Attacks of Opportunity and a chance to fall prone where it is and end its turn. Will it do all that just to set up a flank on you for its allies (that only have a single action to Strike when they get to you from outside your aura)--when you're going to get a completely free non-provoking move next turn anyway?

If it does, I'll take that deal.

Aura Shaper is a mid-tier feat that can expand the size of the aura to up to 30 feet, but earlier, you're trying start a fight by activating your aura and move to something like this

_ _ _ X
_ O _ _
O X _ 👨‍🚒  

where _ is a blank space, X is your opponents, O is your allies, and 👨‍🚒 is you. Your group of allies is clustered to the left of O, and your group of enemies is clustered around the right side of the map, that is, around you, but you're in a spot that has a blank space between you and any of them as well.

Keep your friends far and your enemies close-but-not-that-close, as the proverb goes. You can then use Air and Water Impulse Junctions to keep your action-taxing distance from foes intact when they approach.

As the fight goes on, positioning changes because your allies and enemies get a bit more intermingled, but those position changes are extremely costly for your foes (a decent chance of falling, no chance to avoid reactions because no Step) and free for you (Air Impulse Junction, Water Junction).

It's a really strong effect and it requires some really careful positioning to work well.

Using Weapon Infusion to give reach to your melee strikes helps in staying at a range to be far enough away from your allies to keep from wrecking them as well as Air's tools for mobility (Four Winds, its Impulse Junction, Lightning Dash) to get your positioning exactly right (the water-air kineticist I'm playing is also an Elf with Nimble Elf and Fleet). Tidal Hands and the Water Impulse Junction allow you to push enemies if they get too in your face, which can save your taking a move action and keep enemies at the ideal spot for your aura.

Your frontliners without reach will probably be taking lots of hits just because threats will have to Balance over to you, but in case they do, you'll want to have your Dexterity as your second stat to maximize utility from your light armor to deal with threats and to bolster your Reflex saves. Water's Ocean's Balm and Deflecting Wave feats help with healing and negating damage outright respectively, though I'm skipping Ocean's Balm in my build. If you have Free Archetype, you can go Rogue to get Nimble Dodge against attacks that Deflecting Wave won't cover and Mobility to make your Air Impulse Junction and other incidental positioning bulletproof.

The object in a lot of combats is to use your mobility options to get far enough behind enemy lines to cause havoc with the aura while still being a move action away from your targets. Getting a Slow from a critical hit with an Elemental Blast in the aura also helps eat up actions that would otherwise be used to hit you.

Even if you don't want to be in the mix actively debuffing with your aura and you want to be ranged, the Balance clause makes the aura function as a very strong deterrent zone. Balance requires that you be on uneven terrain to do it, meaning that an opponent outside your aura without reach would need to Stride to the square inside your aura and then use the Balance action to make it the last 5 feet without falling. It's now spent two actions just to get to you and it's off-guard for having taken all that trouble.

I haven't played with it a lot, and you can imagine lots of places where it won't be the best option like profoundly close quarters combat, but the Kineticist has some other tools to deal with those situations too (the options you've already noted that don't synergize with Winter Sleet). It's a truly great option where it's great, and an own-goal when it's not, but making tactical calls is the name of the game. On balance (haha), I'm a big fan.

Update: it's also worded so that if you get an opponent prone in your aura, they can't get back up. Standing is a non-Balance move action, which would render them prone again.