Empowerments:
These need some serious work. In their current state they serve to siphon power away from Starsurge and funnel it back into Solar Wrath & Lunar Strike, which serves to lessen the importance of Starsurge relative to Solar Wrath & Lunar Strike. It's counter-intuitive to spend your time building a resource so that you can cast a spell, only for a portion of that spell's power budget to be dedicated to re-building that resource. Also, because Solar Wrath and Lunar Strike are so defined in their roles (with SW being a single-target filler, and LS being a multi-target filler) the only real mechanical purpose empowerments serve is to push you to cast the other spell in the situation it is not suited for, which can be accomplished in other, less clunky ways. Starsurge is supposed to be the feel-good, massive nuke, and the empowerments that were added to it for Warlords made sense with the Sine-wave eclipse, because the rotation was not about Starsurge for damage, but instead casting as many empowered Starfires & Wraths as high in each eclipse cycle as possible. This mechanic made Starfire & Wrath's purpose in the rotation to be the top priority in dealing damage, and without these empowerments Starsuge would've been dumped at the peak of each eclipse and Wrath/Starfire would have been simple, boring filler spells. This empowerment mechanic no longer makes sense, as Lunar Strike & Solar Wrath now serve the purpose as Astral Power generators, and do not require Empowerments from Starsurge to be given a purpose beyond filler. In addition, with the removal of Scythe of Elune randomly proccing Owlkin Frenzy, the elegant solution of using OKF procs to dump empowerment charges no longer exists, and the problem of requiring some method by which to consume empowerments other than simple hard-casting (which I elaborate on later) becomes a thing.
Problems:
1) Mechanic doesn't really have a purpose within toolkit.
2) Counter-intuitive to build/spend resource playstyle, draws power away from spenders.
3) Accumulation of empowerments & difficulty consuming at reasonable pace.
Recommendation:
1) Complete removal of Empowerments.
2) Increase Starsurge coefficient to 600% Spellpower.
3) Removal of "Empowerment" Artifact trait. (See Artifact trait section for replacement recommendation)
4) Re-design of "Starlord" talent. Now provides X% haste for Y seconds after casting Starsurge.
5) Re-design of "Soul of the Forest" talent. Now increases Starsurge damage by an additional 15%
6) Addition of baseline ability "Astral Shower", giving your most recent Moonfire/Sunfire a 5% chance (doubled on critical hits) to make your next Lunar Strike/Solar Wrath (respectively) instant.
Stellar Flare:
Stellar Flare is going into it's 3rd expansion now, with it having been the ugly duckling of it's talent tier for the entirety of it's existence. It's clunky usability and low damage have consistently failed to present a viable alternative to the other talents it's competed with. The virtually-zero rate at which it is taken had me convinced Stellar Flare would either be removed or overhauled for Legion. Instead, it finally got a significant damage buff that could make up for the clunky usability, but got placed on the same talent tier as Incarnation. Between player's familiarity with Incarnation, it's comparative ease of use, and StF's Astral Power cost, Stellar Flare in it's current state just won't see use again. Not unless it mathematically outperforms the other talents on the tier by quite a margin and becomes the only viable choice. The addition of an Astral Power cost makes it's usability even MORE difficult, as it now competes with Starsurge, Starfall, and Fury of Elune for Astral Power. Fury of Elune has a better conversion coefficient for turning Astral Power into damage (it's close at 1 target, but FoE blows StF totally out of the water at 2+) so these two talents are essentially mutually exclusive. Stellar Flare also makes no sense with Nature's Balance, as the entire point of the talent is about the simplification of the rotation by eliminating the need to refresh DoTs. Stellar Flare doesn't make sense with any level 100 talent except for Stellar Drift, and (ignoring the fact that Stellar Drift is problematic in and of itself, more on that later) that pushes Stellar Flare into this wierd niche role where there's few enough targets that 2-3 GCDs per target can be expended maintaining DoTs, Starfall uptime can be maintained at a reasonable level, and those targets must be too spread out for Fury of Elune to cover. There's so many conditions that need to be satisfied for Stellar Flare to even mechanically make sense as a choice that the skill becomes binary - it either has to be overpowered or it never sees use. This binary situation can be avoided entirely by giving Stellar Flare a niche not satisfied by either Incarnation or Soul of the Forest, and that would be movement. The way to do that is to make Stellar Flare instant, so it can be used as a movement-filler.
Problems:
1) Stellar Flare's astral power cost conflicts with other talents/abilities
2) Stellar Flare's usability makes it awkward to fit into the toolkit
3) Stellar Flare does not provide anything that is not done better by other talents.
Recommendation:
1) Stellar Flare is now instant, and has no Astral Power cost.
2) Damage reduced to (80% spellpower) + (312% spellpower) over 24 seconds.
3) All talents affecting Moonfire or Sunfire also affect Stellar Flare.
Stellar Drift:
Similar to Stellar Flare, this talent simply doesn't provide anything to the toolkit. A radius increase to an already-large AoE zone, a small damage boost to the less-important part of Starfall, and casting while moving. Unfortunately, the playstyle that involves heavy starfall usage (ie. the one you will want to take Stellar Drift with) invovles a comparatively large number of instant cast spells (multi-dotting!) resulting in very, very few scenarios where the player must move and does not have a DoTs within refresh range. It's another aspect where an add-on effect has counter-intuitive usage to the gameplay of that ability. Stellar Drift needs a niche to call it's own, and I suggest using it to address the fact that right now Balance Druids have significant ramp up time on AoE. While that's okay for long encounters, for things like challenge modes, Mythic+, or trash packs, it's a very large inconvenience. Re-purposing Stellar Drift to shift damage away from the Stellar Enhancement and into the direct Starfall damage addresses this, as now the ramp-up time is simply how quick can you get Starfall up.
Problems:
1) Incredibly weak talent.
2) Playstyle & talent benefits at odds.
3) Balance needs a way to shorten AoE ramp-up.
Recommendation:
1) Stellar Drift still increases Starfall radius by 30%
2) Now increases damage by 25%, up from 20%
3) Now additionally removes Stellar Empowerment, but causes Starfall to receive double benefit from Mastery, and have it's damage increased by "Falling Star" artifact trait.
Artifact Traits:
Starting with the "Empowerment" trait - I would like to see it replaced with a trait that increases the radius of Lunar Strike, the twin of "Sunblind" for Sunfire, 5 yards is a terribly small AoE and requires your tank to be exceptional at stacking, a simple 5yard increase from an artifact trait is a huge QoL increase.
Power of Goldrinn - Please replace the particle effect. Goldrinn is an enormous, savage ancient wolf. The puppy pet model flying in a lazy arc towards my target does not represent the ferocity of a wolf ancient.
Echoing Stars - Really, really bad for a major trait. It could literally read "Starfall does 30% more damage" and be functionally better, as then you still gain the benefit on 1 target and don't require 2. My ideal replacement for this would be a talent that causes targets struck by Solar Wrath / Lunar Strike critical strikes while afflicted by Sunfire / Moonfire to explode for ~25% spellpower to all enemies within 8 yards. Another idea, Moonfire/Sunfire ticks have a chance to trigger Owlkin Frenzy. If not these then some form of interaction between DoTs and the remainder of the toolkit. As it stands single target rotation has ZERO DoT interaction (as Shooting Stars is the worst talent on the tier for one target) and this major artifact trait is a great place to shore that up.
Minor Wishlist items:
1) Fury of Elune - Why is the Fury of the Moon Goddess a sunbeam? Blue/silver colour scheme please.
2) Additional utility on Feral Affinity - Feels lacking compared to the other two. Possibly Predatory Swiftness, where each point of Astral Power consumed has a 1% chance to trigger the effect.
3) Re-evaluate Haste interactions - Both FoE and Starfall receive minimal benefit from Haste. Would like to see haste increase tick rate independent of Astral Power consumption rate (ie. Starfall duration is fixed while haste adds more waves of stars, FoE astral power consumption is fixed at X/second while haste increases the tick rate.) Otherwise Haste is lacking compared to Mastery/Crit.
4) More communication with Balance community. Really disheartening to have many of us agree that a problem exist and to see build after build go by without it being addressed, and radio silence. Even just telling us you agree it's an issue and have a fix in the works is something.
5) Re-evaluation of World Drop legendaries. Right now Impeccable Fel Essence is waaaayyy stronger than the others.