mmmmmh... Zenyatta in my mind is a side medic that his healing isn't what you should be focusing on. Sure throwing a Harmony Orb on Mercy is good and what Zenyatta should be doing is being in the second line of the offence with a Tank, that tossing out a Discord Orb on targets is important so the second line can take care of them before that target gets behind your lines and starts messing with your defense. In my mind he's a back up Mercy and that he's focused on keeping that second line stocked up on heals.
Like.... okay, First Line offense heros would be like Tracer, Pharah, Genji, Heroes that can move fast and have good damage output. Mercy would be behind those Heroes giving them the heals and due to Mercy's mobility she can get out if need be. Second Line offense Heroes would be like Road Hog, Soldier 76, Reaper, McCree. These guys are slower but they have deceptive range to them [Soldier 76 and McCree both have good accuracy at long distances and they can move up into the First Line if Heroes there start dying. Reaper can pop in and out of the First and Second Line thanks to his teleport he also is self sufficient due to his soul reaping. Road Hog is there for easy pickings with his Hook and Shotgun combo.]
So How I would organize the support is how they affect these two lines of offense. Lucio and Mercy are great for First Line thanks to the heals they deal out but also the buffs, Lucio with Speed [Very important in the beginning of a Match and for pushing] and Mercy with her Damage boost.
Second line is there for more passive heals and for people retreating from the First Line. in this Case Zarya can also count as a second line Offense with her giving shields and over time her damage boost so when she does move up to the First Line she's all buffed up and ready to rip thru people.
It's funny I like to think of the placements of heroes sorta like soccer... First Line Offense is like Wings and Center player where as the Second Line is more like the Attacking Midfielders. They can push up close almost behind the forward positions where they can keep pressure and help keep from the ball being overturned. [also all three positions of Forward, Mid, and Defense can bleed into each other, that a Defense player can jump up into the Midfield to help out and vica versa.]
One thing that does worry me is when people play as Rienhardt and they have him right up in the First Line. Really Rienhardt should be an offensive defender helping out in the Second Line helping out pushing them up and taking out special targets that slip by the First Line. If the First Line has to retreat then Rienhardt can pop up his shield as Zenyatta tosses Harmony Orbs on people who need it the most. [and if he has his ult then he can pop it give everyone some quick heals so they can jump back into combat quicker.]
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