Diana and many others are limited by the stat options in the runes
I think one of the more serious complaints that doesn't get attention is the fact that runes don't allow you to customize your stats anymore.
Certain champions work really well with certain runes, but are crippled by the stats they give. and vice versa
Take
for example. Every since Diana got her new passive, she no longer receives an attack speed bonus without using a skill. So you were somewhat forced to go attack speed runes to make up for it. But since the only way to get attack speed is by 2 rune trees. You are some what lacking in the options you can play with her as.
I prefer to use Electrocute on Diana, but there is no way to get attack speed anymore.
Another problem behind limiting stats behind rune pages is the lack of armor / defense items. The resolve tree is pretty one dimensional design wise. It gives you options to protect yourself but only under extreme conditions. ( Situational ones like +10mins to get bonus armor and MR , ) Making unappealing for people to get if they want to protect themselves in laning phase. And since they you only get health rather than overall armor or magic resist, means your going to take a lot of damage from champs than you would be before the runes rework.
Overall I personally, and maybe a few others, would like to have the option back to customize the stats runes give you. Cause they play a bigger part in the early game advantage than the KeyStones for each rune page.