Tldr at the end.
Problem:
The long DPS queue times are due to a lack of healers.
While there are several issues for healers, I want to address the biggest one:
MMR (or MMV)
All data shows that it is much harder to climb as a healer than it is as a dps.
For example, the dps to healer ratio for the top 100 players on the ladder in solo shuffle is 98/2 (source: seramate EU UTC+1 13:20). In a perfect environment, it should be around 67/33. (assuming a lobby consists of 4 dps and 2 healers with 6 rounds played)
Solution: Decrease healer mmr loss
First case: Draw for a healer (3-3)
Implement an exception in the MMR calculation for healers. Never lower the MMR in this case. Even if it makes mathematical sense, from a gameplay standpoint it improves perceived fairness due to the lack of agency in the game for healers. If there is an increase in this case, leave the MMR gains untouched. This would result in a net MMR inflation for healers.
Second case: Defeat (MMR Loss)
To get a healthier ladder, the MMR loss calculation for healers should be tweaked by lowering the loss value. I suggest starting with an amount like 10% and then observing the inflation. For example:
Old calculation:
From 2074 MMR to 2030 MRR = 44 MMR loss
New calculation:
From 2074 MMR to 2034 MRR = 40 MMR loss
If these are not placement games, let the CR catch up.
With ~127.2K games played per day (source: check-pvp/Players activities EU), this would naturally inflate healer MMR, resulting in lower DPS queue times. Obviously, the amount could be changed to 5%,15%, or whatever depending on the desired result. This would produce a net MMR inflation for healers.
There are undoubtedly many more things that could be done to get healers to queue more (additional rewards like mounts, gold, etc.), but those are not part of this topic.
Thanks for reading!
Tldr: Reduce the MMR loss for healers to reduce dps queue times.