If you absolutely MUST change Diana (long read)
I just started playing this year, I'm unranked, and usually a 'guest' forum lurker, and I care enough about this topic to actually emerge from the shadows. Obviously, with the frequency that this topic is brought up, people care and are highly intrigued by the Lunar Princess, and even Riot says she needs some changes. A lot of the suggestions I've read centers on scrambling her kit. This makes me cringe, because the thing that attracted me to her in the first place was that she had an 'ult' on low CD that made her actually feel like she had 4 abilities, where most champ feel like they have 3 with a bonus fourth that comes around once in a 'blue moon'. See what i did there? There is a way to redo her, (actually enhance is the better word), without breaking her, and move her to a place that will make her very good in the new jungle you are thinking of doing.
Her passive is way under rated and should be central to her gameplay. 'Assassin' Diana doesn't usually take advantage of this, and this Diana is usually the one people complain about ( Q>R>R, Rinse, Repeat?) While most call this identity crisis, I see this as flexibility in build. Tanky or assassin, in between? She is a seeker of ENLIGHTENMENT, she's a rebel, there's a lot here to work with. I will first outline smaller changes to her existing kit, then introduce two huge ones that will give her HUGE differentiation and utility.
Q- No change, this isn't her problem. W-This is her problem. Have her shield scale with health, MR, or armor, maybe a mix. Make people invest in Defense if they want defense. It currently allows people to build glass canon, and still have survivablility. Allow her damaging spheres to continue to scale with AP. Also, increase ratios in each part of this. E- This is already on the PBE, have her E reveal stealthed units around her, She becomes the anti-HIDDEN champ, no more lies!! Seeker anyone? All targets in an area exhibit a Moonlit Glow for the duration of the slow. R does not reset off of this. Also proccs her passive on next AA after E. Sorry Teemo, no hiding. R- Take some of the base damage out of her ult, discourage Q>R>R (you have been slain). Because that's what happens. It is now a dash with some damage, not damage with a suicidal dash.
Now for the big changes. Mana is no more on her. She now has Luminescence. In her tooltip, it says if she dashes to an enemy afflicted with moonlight, she CONSUMES the moonlight on all non target ememies. Where does it go? (her hips bu dum cha). Make her farm it. She gains luminescence when Moonlight debuff is consumed. This will make her try to hit as many minions or jungle monster with her Q to keep her resources up. This will also make her more mobile during her laning phase, since the dash still resets. Positioning will be key. She also restores a PERCENTAGE of MAX Luminescence for KILLING a target exhibiting a Moonlit Glow. Harder to farm, but with more benefit.
She also now has a new ability enhancement, Lunar Blessing. It is available at level 6, with a long cooldown so it feels more like a 'traditional' ult, (though Diana doesn't give a sht about your traditions). It can only be used on Q and E, from pressing ALT+ (ability).
Eclipse-On Q cast, can be cast on ALLY, NEUTRAL, OR ENEMY CHAMP. (can still be used on multiple targets) Non damaging Q animation. Allies are stealthed (cloaking anyone) and can only be seen by true sight or enemy champions. MOONSHINERS? Allows you to smuggle allies through heavy warding for a duration of time. Think of a castable Evelyn's passive, (cannot be self cast). Cloaking ends after duration, when ally goes too far from Diana, or when ally attacks or uses an ability. Jungle Creeps- With the new importance being placed on Baron and Drake, this will make it harder to smite steal since the enemy will have to either pink the pit or actually face check it to try and steal. HUGE baron control. Also imagine the new Baron bait; no more just trinket warding to see if the enemy team took it. Ememy cast- Removes minimap vision from afflicted champ, and also cloaks afflicted champ from the enemy team vision for a duration, (think graves). You kept Diana in the dark, now its your turn Leona.
Full Moonfall- On E cast, reveals a larger area around Diana, giving all targets Moonlit Glow, pulling and slowing all targets in her normal sphere of influence, and slowing all others that had been revealed. This would function like an empowered Quinn E.
These changes would keep her kit identity intact while giving her more utility, enhancing her character identity, giving slightly less damage, and encourage teamplay. She would bring so much to the team, while have less single target tunnel vision. The Lunar Blessing portion of her kit, will seem OP, but it must be used wisely, and at the right time to even be useful. It would be easily wasted and highly specialized, while remaining flexible. This may make her pick or ban, but you will have to be an exceptional decision maker with great team communication to really use her potential.
I trust you Riot, I think you guys are doing a bang up awesome job. I just had these ideas and thought I HAD to share.
(I'm sorry if this includes anyone else's ideas, I've been reading so many ideas, if they bled into this, it wasn't intentional).