Most of the runes aren't really high damage compared to the stats you gain (And here's some numbers)
So I did some math on the runes and threw together some random observations I had on how valid the 'it's so easy to snowball and harass in lane due to the rune's damage!' complaint actually is. And it ends up the problem isn't with the actual runes themselves
It's 15/25 AD/AP from picking sorcery, or 11/18 from domination, and precision's keystones. Otherwise it's all pretty much okay.
For reference:
At level 1, Electrocute deals 50 damage in 3 attacks. With the 11 AD from domination is does 55.5. Taking into consideration the 50 second cooldown on electrocute, as long as you auto attack once every 10 seconds, or more, the 11 AD will do more. With AD scaling abilities, the 11 AD does even more. Cheap shot is pretty good if you're high CC in domination, the 12 true damage is equivalent to around 15 physical damage (your base armour reduces by around 20%) every 4 seconds but good luck hitting CC whenever it's off cooldown then an auto attack or another ability on top of that. Eyeball collection gives 0 AD.
At level 1 Arcane comet does 30 damage, with the 25 AP from sorcery it becomes 35. With a 15~ second cooldown (use abilities to harass and reduce the cooldown every so often), you need to do more than 23.33 damage per 10 seconds, so the 25 AP gives you more damage if you deal 93.33% of your AP per 10 seconds on average (So maybe E twice as cassiopeia every 10 seconds). Absolute focus gives you like 2 AP, celerity gives 0 AP, gathering storm gives 0 AP, scorch is like half an arcane comet (So if you have it, E three times every 10 seconds as cassiopeia and the 25 AP is better!)
TLDR; The rune combination stats for sorcery and domination are equal to if not outright better than the keystones themselves early game, hence the snowballing
Then there's precision. It's much more complicated than I can analyze by straight up giving you guys numbers but here's the gist of it:
Press the attack doesn't 'compete' with the combination rune the same way Electrocute can be outclassed by the bonus AD. The AS from picking precision just makes it easier to proc. They synergize rather than adding on top of each other. Then they have the vulnerable status, and it gets complicated when you're the ADC and the support also gains +12% damage. Let's pretend the enemy is desperately trying to escape, and you get this vulnerable status off (which straight up deals 30 damage) plus one measly auto attack more from you and your support both at 50 base AD before they disengage. That's 42 damage and I can't see any cooldown so this isn't limited like arcane comet or electrocute so even at worst it is still stronger than arcane comet (because if the enemy bot lane disengages and doesn't come back for 20 whole seconds, arcane comet's cooldown is back up but so is press the attack. Earlier and press the attack is much better because arcane comet is on cooldown)
For lethal tempo, AS is complicated in that you can't compare it DPS wise the same way I compared AD to electrocute earlier. It has a negligible effect in terms of damage per 10 seconds unless you say the ADC is standing still attacking a dummy the entire time. But in general, the 18% AS bonus from picking precision is very slightly better if you harass with autos, for all ins unless the fight manages to last longer than 12 seconds, or if the enemy you were attacking escapes and someone else is in your range, lethal tempo will be much, much better. I can't really say how much this is worth compared to Press the attack, electrocute, etc but if it gives you an extra auto in an all in (champs have around 50 AD average) nearly as good as electrocute for that all in (with its 55.5 damage). (with a lower cooldown. So it's actually better.)
As for the non-keystone runes, alacrity gives 3% AS, and the first three masteries are fairly complicated and I can't analyze them easily either but 5% increased isn't going to be worth very much until late game. (With rank 5 Ashe W, it is worth more than 15 AD if you already have 220 AD beforehand, bringing your 80 base damage to 300 total damage. For 10% increased damage it's 70 AD, which is still a lot but still not close to early game)
I think they're trying to force a late game stat onto an early game advantage (18% AS. But you only focus on AS and crit after getting BF sword on your first back.) and should instead just do something like 12% AS + 15 damage on hit and give reasonable nerfs to the keystones
TLDR; What the hell is going on with these precision keystones? At least make them consistent with the sorcery and domination in that the free stats are good early game and the keystones themselves aren't extremely strong
EDIT: yay due to one downvote probably no one will ever read this post, and that downvoter didn't even care to share why he disagreed! Isn't it just great when one guy can literally silence your voice anonymously?