The problem with me watching Heroes streamers on Twitch is two folds:
1. All the current streamers are just not really that diverse or fun to watch. Compare it to Hearthstone where you have so many streamers with different personalities that fill different niches. Trump (more family friendly), reynad (lots of salt, great stories), Forsen (dank memes), Amaz, Hafu, Kripp, Rats (arenas), Kolento, Strifecro (ladder), etc. In Heroes its pretty much everyone doing the same thing. There simply isn't much to enjoy as they basically are either going to rank 1 or climbing up to rank 1 in Heroes League. There's nothing else beyond that or a different mode that encourages more diverse gameplay or interest. I know they're adding Grandmasters and Arena mode in 2016 but that's still a long way too go.
Khaldor is probably my favorite Heroes steamer except that he pretty much only casts EU games. I really wish he played more because he has the most interesting personality out of all the Hero streamers. I mean when something exciting happens, he's actually excited. No offense to Grubby, SolidJake, ZP, all the other TempoStorm and Cloud9 players I watched stream, but they sound exactly the same. I've literally falling asleep watching Hero streams several times.
2. I rather play Heroes than watch it and I'm not a big fan of running a stream in the background while playing it mainly because there's no point in it. I'm not gaining anything from it and neither is the streamer (because I'm not actually even watching the stream or further interacting with the streamer or chat). With Hearthstone, I will 100% when playing listen to the podcast, a YouTube video, or someone stream. Never play Hearthstone in full screen because its rather pointless.
When I used to play League very casually with my friends, I would never watch or listen to something besides the game itself. Why? Well, a game can lasts 40 mins to more than an hour, its tiring as hell after playing a couple hours. Because of the game length, sometimes I just don't want to play (lazy/tired after classes/work) so I will watch some League streams and play something like Hearthstone or do some easy homework.
With Heroes its completely different. Games last from 15 mins to like 30 mins at max. I can play them in small bursts (a couple here and there). Could watch someone stream for an hour or I can play 3 matches of Heroes. Its just that recking people with Jaina seems more fun that watching someone play.