If tanks and healers are in the same bad they shouldn't be. Tanks and warlords should be in the same bag, same exact restrictions. Healers are absolutely fine.
Warlords don't impact with the damage, they impact with having 4 stuns they can cycle non-stop and having parry stance making them have 2k pdef 1.6k mdef. Add a bishop with balance life and a OL to that equation and you have a guy that only dies with 15 people hitting him. Now add 2 aoe dps that just follow the warlord or 1 aoe dps that follows 2 warlords and suddenly you have a party that has 1 or 2 cc TANKS tagging everyone, 1 or 2 dps getting dmg/kills and 2 support always pumping heals and pumping the party score like crazy. When this setup gets you easily 50% more score than any other setup then you start seeing 3, 4 or 5 groups like this per map and it's why you have 10 warlords in a team.
If you want to change warlords, limit it to 1 per group, increase the reuse on all the stuns by 1 or 2 seconds and increase the mp consumption on parry stance so you can't have it on permanently.
The problem you had with your elo algorithm this season was obvious. For some reason it tried to equal 1 high elo player to 2 or 3 lower elo players instead of prioritising moving the players between factions. So you ended up with 40 players with a total of 200k elo vs like 60 with a total of 200k elo. If you put the class balance change in it will probably fix it but it shouldn't need to be tied to a class. In previous seasons I remember my clan ALWAYS having people being moved to the other faction for balance and we never had these imbalanced numbers.
My last advice is that you take in consideration that you're implementing changes that mostly impact high population events and that's not the case anymore. I can't imagine you will be able to gather any sort of useful feedback at this point.