It's really nice to have solo ranked back, that being said here's a couple things I'd like to see changed

1) Mixed Realm teams update
is no longer primarily to fill gaps on one side to start games, it's to make even fights and avoid 2x of same classes.. e.g:
if Order has 6 players at 100 MMR and destro has 6 at 200, 3 Destro and Order will switch sides to get both teams avg MMR as close as possible.
Even if you don't want mixed realms as anything other than gap filler, I just had a game with 3 slayers and 3 doks and it could use some improvements:

Actual Game
Destro Avg MMR - 970
Order Avg MMR - 544
MMR Diff - 426
Highest and lowest DPS switched (Slayer for slayer - only order on destro team was 1 slayer, so could have picked the one narrowing the gap the most)
Destro Avg MMR - 821
Order Avg MMR - 693
MMR Diff - 129
Closest Possible : highest and lowest DPS switched, lowest and lowest healers switched
Destro Avg MMR - 757
Order Avg MMR - 756
MMR Diff - 1
While more complicated algorithms could be implemented to get the closest MMR match.
But I think the easiest way to get good results would be to sort by Role then MMR and..
Then team 1 picks top MMR first, team 2 picks 2nd and 3rd.
From this point on if team 1 has higher avg MMR than team 2 they will pick the lowest MMR of next role or highest MMR if they have lower, alternating to pick a player until complete.
For this particular match that simple method would keep the MMR team difference between 14-37 MMR, depending on role sorting order.
Doing this should also allow you to have players of much higher MMR compete with low MMR players, as the teams' overall MMR difference would be much closer, meaning you won't have good (hardcore ranked) players stop playing because they never get a match after getting too high MMR.
Where team MMR difference does not exceed 100, priority should be given to avoiding 2x of same class in same role on one team.
This will also have a further impact on reducing side stacking.
You've already opened the bag lorewise, might as well make the most of it, also mixed teams are so much fun

2) Problems getting the ring..
A lot of players are motivated to play ranked by the prospect of attaining the ring which unlocks some BIS gear combinations.
Right now, unless you happen to play a lot doing EU prime or you are part of the Group ranked community, the ring is almost impossible to get or could easily take over half a year.
This is a bit much for a single item, even if it is very good, and so what would have been a driver to get more to queue ranked doesn't have the full effect since most won't be able to get it regardless.
Most players will need 50+ games to reach 1K and then another 100 at 50% winrate to get the insignia, and while that's only 2 games on avg per day for a season, not every day will have a match when you can play or some other event like city, fort, guild event will take precedence.
And if you wanted to play more classes (I've got 4 ranked ready) you'd have to play 8 games a day on average or as I'm doing now.. stick to one class for an entire season or two (losing out on weekly rewards and more likely getting burned out).
Not to mention some classes are much better at reaching +1K (Slayer/knight vs BW/SM)
To solve this I propose the following:
a) increased ring insignia cost to 100
b) make weekly reward give both the insignia AND emblem for all tiers
c) all solo ranked wins gives 1 insignia, removing the +1K MMR requirement
d) all grouped ranked wins gives 2, losing gives 1 (this will retain the reward benefit of group over solo)
Yes, for a good player it now takes almost twice as many games to get the ring from solo, but for everyone else it is attainable as long as you win enough games and the frustration of losing MMR, being stuck below 1K MMR is gone and having your MMR reset at end of each season.
3) Remove pre-season
It seems somewhat pointless, unless you release balance changes at end of primary season and then tests and further changes until next primary season. Better to have longer seasons otherwise.
4) Remove MMR loss for missed pop
While I get the idea of preventing dodging strong opponents to boost your MMR, this at least with suggestion 1. of mix realms becomes much more unlikely.
Instead make it a 1 hour Quitter and if you feel further deterrent is needed you can de-prioritize them for games for a full 24 hours (i.e. even if somebody else of your role queued after you, they will still get SC pop before you, unless you are needed to start the game)