Tough one. Both heroes have great mobility and can survive pretty well. Lucio: pro:

• unique team mobility - great for slow tanks like Zarya and Hog.
• great ult to prevent instant team death - best against Junkerqueen
• can boop dangers away like Bob or Reaper ult.
• good option to deny enemy team from taking control of a payload Contra:
• Lack of burst heal makes it easy for DPs like Echo to take out the team one by one, starting with the other support
• bad when the team is split up as it happens often in lower ranks

Mercy: Pro:

• very good damage boost
• very good at keeping teammates healed while staying out of the enemy’s sight
• res skill
• very good at staying alive with some skill Contra:
• considerably less value if they have to pick up the slack of the other support and do the main healing
• very bad survival qualities when being last woman standing compared to other supports

I would think that Mercy would be quite decent in metal ranks and giving less value at a higher level when Ana/Kiriko/Zen get more prevalent. With Lucio, you might only see him shine when being out of metal ranks.

Only place 12 - work to do

Personally, I would go Zarya and maximize charge easily against their DPS and just burn their world down.

Ameizing

Tank is hog, Ball and fist. Dps is Genji and support is wifeleaver and brickshit.

I am not surprised. I saw that coming from a mile when they announced that one tank would be dropped. It is just too much responsibility for one person, and it is uncool for one trick ponies as the meta shifts to different heroes all the time. Also, the awesome synergies between tanks are gone.

Well, please bless me with news when the actual book is being published.

Tl;dr: this wall of text tells you that you need to provide for yourself because we won’t. You are welcome.

Actually, the vast majority of EZ lines do come from people who have been carried on the winning team.

Make Torbjörn be able to program his Baby, pardon turret, to put proper priorities e.g. always ulting heroes first, then supports etc. , not hitting sleeping heroes etc…

They could have just nerfed shield strength in OW1 or double shield cooldown if both tanks go with a shield tank.

Not enough

Well, sounds like the main difference to lower rank is the aim - if you kill the others faster, you are never out of position.