Regarding OW, a lot of what made TF2 attractive has been scrapped in the name of making the game "accessible" to casual players. That's fine of course, but it unfortunately makes the game less fun to watch at a high level. For example, there is almost zero skill required for advanced map traversal (save for Lucio). In TF2 on the other hand, rocket jumping and sticky jumping are non-trivial, and are critical for map dominance. Another thing I find weird is character caps. The goal (in theory) was to ensure that there was variety int the meta, but it doesn't look like it's working tbh. It also shows that Blizzard doesn't really trust the comp community to independently minmax strategies for team comp.
Let's not even start talking about the collectible system. TF2 does this masterfully through the trading and crafting systems. I can get every single item in the game without spending a cent, including cosmetics - without relying on RNG of course. Blizzard on the other hand is in it for the $$$. Have you ever heard of a card game where you can't trade cards? An absolute joke!
But Blizzard is doing quite a few things damn well. Most prominently, their approach to openly communicating changes and stuff that's in progress is very refreshing imo. I hope other devs learn from this approach.
[1] http://sullygnome.com/temp/bd061c88-c4f9-4f70-9231-a5089bbd7...
[2] http://sullygnome.com/temp/d49580c6-7a16-4601-915b-df42bc752...
Dwindling twitch numbers doesn't always mean a game isn't fun to watch.
What? I've watched Hearthstone and Overwatch on Twitch several hours a day since launch and I will probably never be bored. They are by far the best streaming games out there IMO.