DIANA, scorn of the moon: my proposal for a LOW SCOPE rework!
Hi everyone, i wanted to share my suggestions for a Diana rework. Like all the Diana rework threads, i think that swapping her current E and R is the most reasonable solution. This is kind of a long read and i pretty much know my post will much likely go unnoticed, but i want to sincerely thank everyone taking his time to read this.
What should Diana be?
I think we all agree that her assassin pattern is problematic and, honestly, not very engaging. I want to shift her more towards a diver/skirmisher identity. I envision her to be an agile fighter that during a teamfight can reposition herself on various enemies with her Lunar Rush (think of a conditional, gated, champion-only, not-retarded version of yasuo's E). Diana's niche is now to group enemies together with her new ultimate, and so she is a desirable pick in wombo combo comps.
What should be her damage pattern?
She will keep her stickness with the Lunar Rush reset mechanic, but lose her burst potential. In order to make up for the damage lost, Diana will be able to play around her passive more, gaining DPS and survivability. Obviously if she is going to be more reliant on her AAs she shall need enhanced base ATKspeed and movement speed.
Why the true damage?
If you read the kit i propose, you will probably notice that her passive and E deal %maxhp true damage. I know that on those boards there is a general resentment towards this type of damage, but please let me explain my decision. If she's supposed to reposition herself several times during a teamfight by jumping on different enemies, she will need tools not to feel awkard in the face of a tank; adding %maxHP true damage will allow her to deal significant damage on beefy targets without being burrsty towards squishies. This true damage is obviously moderate (no Fiora stuff, for sure!), as she isnt meant to be a tank-buster. Moreover, if only 2 of her 4 damage sources are magic damage, penetration will be much less effective on her, further reducing her burst potential on squishies, and allowing her to build the likes of Berserker's Greaves.
What should she build?
She is encouraged to build AP and discouraged to build tank items. This is achieved with: low base damage, low scaling base damage, no CC on low cooldowns, good ratios, and her survivability concentrated on a high ap scaling shield (a design principle similar to Riven's shield). Those design principles are the same that killed off tank ekko for good. I think she should be comfortable with an ap bruiser build with core items Nashor's Tooth and Lich Bane. Her build should look like:

In what lane should she be played?
Since now Diana has her Lunar Rush available pre-6, she will be less underwhelming to play in lane. She will also be a significantly better jungler. With a more DPS-oriented damage pattern, she will be better against fighters, but less efficient at trading with mages. She will keep her current anti-assassin identity through her shield. As she has no real escape nor high tankyness she will be unsafe in a long lane.
Major changes:
General: high tier movement speed (345-350), very high base atkspeed and scaling.
Passive: deals base magic damage on hit with some scaling, and additional %maxhp true damage on 3rd hit.
Q: Damage crippled. Greatly reduced cast time (i want a much more fluid gameplay). Moonlight debuff will grant vision and even reveal stealthed champions, but can only affect champions and jungle camps. She will lose her QR on minion ----> R on champion, but i feel this is necessary as she would have way too much aggression potential in lane, as now her gapcloser is available pre-6. For this exact reason i belive it will be necessary for her Q to have an high cooldown early, greatly scaling down with rank.
W: spheres spin much slower, so that Diana doesn't get the double shield so reliably. Low base but scales A LOT with AP, i want the shield to be what keeps her alive in a fight, as long as she builds AP. High mana cost early for aggression concerns.
E: Lunar Rush (her old ult): Diana becomes untargetable and dashes through the target. The untargetability on such a spell is almost useless, but i think it offers a good amount of outplay potential and allows Diana to better suvive ambient damage in a tf. The "go-through" part facilitates her autoattacking for passive. This spell deals very low base magic damage and low %maxhp true damage (think about 2%). If lunar rush hits a target with moonlight debuff, the buff is consumed ONLY ON THE CURRENT TARGET and Lunar Rush cooldown is reset. Diana can now dash freely on everyone that has been hit by her Q. The damage on this spell is GREATLY reduced versus live.
R: MoonFall (her old E): Diana becomes invulnerable as she charges briefly. After the charge, every enemy in ult range is pulled towards diana and slowed afterwards. The range should be so that ADCs autoattacking Diana should feel at some risk (i'd say around 600).
Those changes are almost minimal but i think they would be very effective. Being the suggested rework Rek'Sai scope, it could be done in a very small amount of time with moderate resources.