Well, she would be right back where she started. In addition to the cries for every aspect of her kit to be nerfed, the masses would hang DBro out to dry because she's no longer a viable, solo healer again. I always thought she was decent at keeping one target alive with BM, Overflowing Light, and Rewind/Storm Shield -- not as good as the other healers obviously -- but after the scaling changes her Q tickles the tanks.
I never played Tyrande to be a heal bot, in fact I dropped her when they made that change despite her being OP now. I played her for her stun, teamfight initiation, fucking over invis heroes and long bombing Abathur with double birds from downtown. There's cheeky shit I miss doing with Shadow Stalk (Walk , whatever) that you can't do anymore without the enemy team reveal.
Using Quick match to determine a heroes balance or viability is terrible. There's going to be heroes that are viable in low and mid level play, there's going to be heroes that are viable in mid and high level play, and some that are only viable in high level play.
The only way they can really improve QM matchmaking and continue to make interesting non-standard heroes that sort of defy the rigid class roles is to drop blind pick queue is to switch over to a 1 min draft mode without any bans. People will make as shitty decisions as the matchmaker currently does but it will simplify the matchmaker's job of finding ten players all in the same relative skill cap and close enough to the same server in a relatively short amount of time. You would ease the burden on MM and place some of it on the players.
I don't think her healing is an issue. Neither is her damage.
The problem is she has 2 talents that reduce cooldowns. An owl one, and battle momentum.
Her trait is also a way too strong, given the current state of the game.
Then we have the stun, which... isn't limited to just Tyrande.
The changes to the hero scaling threw so many things out of whack.
Stuns are a problem related to the talent system and the removal/lack of items. In Dota you can proactively deal with stuns once you farm up enough gold to buy an item called a Black King Bar (provides magic immunity, starts at 10 seconds and decays with each use until it hits and stays at 5 seconds). In HotS there are so many stuns and only one proactive solution, an Uther ult. A few supports have cleanse, it used to be a proactive solution to dealing with stuns but now it's reactive. And reactive is too damned late with how quickly some heroes get blown up now.
The Sentinel talent is skillshot related so I have less of any issue with that but Battle Momentum is one of those older generic talents and those are so problematic in this game.