If you time Cass R you can dodge it, not watching in to it. So try to stand with your back to her, when she uses R. Early you can abuse her, if she misses q's you go all in and win trade. As you say R is a skilled matchup so it's indeed true that if she hits R and W you might die. But it's not impossible to dodge it either, so if you play well you should win if she plays well she wins. That's what i mean with even matchup. Better player should always win not better champ.

Hey, I personally have never used dark harvest mid. I know it's a common rune to use in the jungle tho. I think HOB and ELEC outperform in the midlane cause you need some tools to play the lane. While jungling can be more afk farming and indeed scaling the stacks as you suggest. So to conclude I like your thought proces, but I think you miss out on damage and utility in lane, and or even in skirmishes when helping teammates, early and mid game. I feel like the game has become very fast pase so winning early and mid game will result in winning more games. Scaling is nice, but I think it will take to long for the Dark Harvest to outperform the other options. Like for an example I started playing for jungler as much as possible sacking waves for it, but I feel like being an assasin isnot about scaling and carrying anymore, cause other roles scale better, you need to make impact early and mid game to be able to "hard carry" games. Hope this is a good answer on your question. Thanks for the comment and positivity :D <3