Wait, you are saying just because some heroes aren't being used, that is bad for the Esport scene?
Yes? Well no, the eSports scene is already pretty lackluster, but I'm sure a few more heroes being viable than the current "meta" heroes wouldn't hurt.
Not every hero needs to be viable when you got enough heroes that ARE.
This is just an excuse for poor game design. Either that or advanced stockholm syndrome.
Take a look at Dota 2's hero diversity, even with a very stale patch they regularly see over 90% of their heroes used in competitive games. HotS couldn't manage that even if you doubled the hero pool.
Also, we got a big year now in favour of supports. Most, if not all supports are viable, and are used in one draft or another.
Who said supports aren't viable? The problem is in HotS "support" is synonymous with "healer", which leads to the meta we currently have.
It's been said time and time again, but "support" heroes should be more utility based, like Tyrande and Tassadar. Kharazim is almost at that point after the most recent nerfs, but heroes like Morales and Auriel still exist where the teamfight is decided based on whether or not they survive, rather than what interesting individual plays they can make.
I do feel like I'm talking to a brick wall since you seem to favour HotS in it's current state. But compare gameplay between a Tyrande and an Auriel or a Morales in a teamfight and explain to me, visually, what they provide that the viewer can see and say "yep he's really good".
Of course it's unfair to just point at those two heroes since they are the worst offenders, but there are many other cases where gameplay mechanics have no visual feedback and are not exciting. Coupled with the very artificial, very binary comeback mechanics (aka no struggle to crawl back, but rather a teamwipe followed by a core rush, maps like Towers of Doom and Hanamura are slight exceptions).
Yet I play this game regularly and at a decently high level, because it is fun to play, it is just painfully boring to watch.