Edited for clarity
So there seems to be some confusion over STORM league. I want to lay out some things to make people understand it a bit better and show them that this will literally benefit everyone (Yes including you who BabyRage about HL only).
I think the confusion here is the fact that blizz hasn’t shipped the final product. They told us in reddit blue posts and AMA (https://www.reddit.com/r/heroesofthestorm/comments/b2muj6/blizzard_please_do_not_use_tl_mmr_to_seed_the_new/eituxsg - for example was posted 1 day ago) that they need more time, but in future patches we can expect the option to toggle solo only and also have separate MMRs for solo vs party queue. What this means as a whole:
A solo only queuer can get a match with another solo player who opted to also fill teams. This is NOT the same as separate HL and TL. Storm league will drastically improve queue times and matchmaking for solo only players and solo players and party players. Everyone will benefit.
Regardless of whether you queue solo only or queueing solo (but not solo only ), you will be working on your solo MMR. If you opted into solo only you will only play against other solo queuers (regardless of whether they opt solo only ). If you didn’t opt into solo only , you can match into games with solo queuers and/or fill parties. Regardless of what you matched, since you queued solo (even tho you are filling a team) you will work on solo MMR.
Ideally matches still prefer to match parties against parties, however, putting everyone in the same league allows a little more mix and match to improve queue times and matchmaking all around. This will actually benefit everyone for queue times as well as fairness of matches.
People who care most about solo only will have improved queue times and better matches. People who want to queue solo but want faster matches can also do that. People who want to queue as a party can also do that.
Furthermore, someone who plays alone can display their skill with solo MMR, which was determined only by queueing solo (regardless of whether they ended up playing against other solo players or against parties, it is a showcase of individual skill).
Overall, bigger competitive population means better queue times and better matchmaking. And this is literally what everyone has been screaming for and wanting.
OVERVIEW:
Three populations will be intertwined providing best matchmaking for all three
(pictorial view below in the comments @drothvader):
solo only → can play against solo and solo only
solo → can play against solo only, solo, and party
party → can play against party and solo
solo only and solo have “HL MMR”
party have “TL MMR”