Hello there, Mr Gustaf.
I might be late on the party but I stumbled upon your analysis, and I raise for you one of my old threads from the dead:
See, I perfectly understand the difference between Tristana and Graves, one has utility AP scaling spells, the other has AD scaling burst damage, and sometimes, you want your AD carries / bruisers to hurt with spells aswell to open new gameplay possibilities right ?
Problem is, you kind of pigeonhole their builds into building AD. That's a race to the scaling and everytime you neglect attack damage, you fall behind. As a consequence, most of your "alternative" itemization becomes a burden. Item diversity just got hit as a repercussion of this "good idea". You would buy a Sheen because your kit allows you to proc constantly, but...
None of your spells scale AP. You lost a considerable 435 gold value, aswell as putting your damage behind.
Let's check the armory for a little moment and list stuff that actually uses "different" methods of damage:
-On-hit (Wits end, Ionic spark, Madred)
-Debuff application (Mallet, Black cleaver, Red buff)
The latter aside, I guess none of these really suit our Graves, right ? Nor does it suit Varus or Caitlyn or Vayne.
This is where attack modifiers come into play. Just like Parrley gives Gankplank a reliable damage spell which also procs all the items mentionned previously.
If we can find a reliable way to link Autoattack to spells, we might actually solve the problem.
Shyvana's twin bite, for example, is really good at doing this. It attacks twice, and resets your autoattack timer; which means you can hit 3 times in less than a second, that implies applying 3 on-hits, proc a Sheen, and, in her dragon form, apply those in a AoE.
Now, all we have to do is find a way to create new forms of "attack modifiers" that would act like spells. Caitlyn's ultimate used to work such a way; it applied Sheen procs and other debuffs, but was reworked. She could not build Trinity again, which drastically limited her itemization possibilities.
Back to Graves; tinkering with buckshot. Imagine this:
Graves fires three bullets in a cone, dealing physical damage to all enemies in their path. Enemies at close range can be hit by multiple projectiles, but each bullet beyond the first will deal only 35% damage.
Now, consider each of the bullets an extension of your autoattack: it deals a percentage (could be below or above 100%) of your current autoattack damage and applies on-hit effects. Think Twitch's ultimate in 3 directions.
Miracle: you got Sheen procing directly on your spell, but also a wide Debuff application (each projectile applying Frozen mallet for example), and a triple on-hit application whithin melee range. Not only that, but a potentially ridiculous close-range Tiamat build strategy.
Once you get this done, you are free to add AP ratios on top of that (because it already depends of your autoattack damage), making AP/Hybrid builds somehow viable and further improving diversity.
Also, Sheen's AP is not lost.
As a final note, I know crits are also part of the problem since they scale exponentially with AD. But that is another story and I can't really think of a solution right now.
Another example: Compare MF's E and Varus E:
Varus has around 85 less base damage and catches up with 141 bonus AD. Late in the game (say +200 AD) it will do 35 more damage than MF's E, which is ridiculously unnoticeable compared to his other sources of damage. Draven has 0.5 on his E aswell, with 210 base damage... The question is; Why would you remove an AP ratio to add weak base damage and inconsistent AD ratios ?
The AD casters and AD scaling champions in general try too hard to fit in a game where AD was not designed to make skills scale.
Adding more AD-caster friendly items would sure solve the problem, but at the cost of hurting Hybridation which is a long-forgotten art. It was meant for hybrids to have both decent autoattacks and spells, AD casters merely stole this role
What would have been the not-so-lazy answer to this problem was to reconsider AD scaling as a whole, and considerable change the mechanics of AD caster's abilities.