They actually are all fairly similar in terms of the role they play in a team comp, but it might not be quite so obvious if you’re used to the labels Overwatch has used since release.
For example, Sombra may seem the most out of place, but consider what role she played in triple-Damage Hammond comps, how similar that is to the role Mei plays in other comps, and how support is traditionally defined in hero-based games (ie, control/damage heroes with 1-2 non-selfish abilities). Note, according to classical definitions, tanks are a subclass of supports, so those two things aren’t different. The “Tank” label is Overwatch is more like the “Warrior” label in HotS before the role work (ie, tanks plus bruisers). Also note, Zarya, whose kit is basically identical in HotS, is labeled as a Support in HotS.
As far as reworks go, it all depends on what you mean by “minor” or “major” reworks, because mostly all it would require is shifting these heroes to the 200 - 400 hp band with some damage tweaks. Basically, make the control damage heroes a little more tanky and the off-tanks a little more damagey. Some ability reworks would be good, but not essential. My very long opinion on the matter is here:
Whether or not that would improve queue times, I don’t know. But, it is how the game is usually played. So having the roster more accurately reflect gameplay seems like a no-brainer to me. It is certainly possible that by expanding the off-tank role and making it feel more like the damage role, that that will draw more players into the Tank+Support queue, but that’s hard to say without testing it.