I kind of agree with the sentiment that Mercy and her existence drives many things in the game, but thats about it.
Right now, yellow is in a place of “balanced imbalance” as being one of the most “volatile” colors in the game. Tons of converters that use yellow, tons of things that make yellow specifically go away. This is slowly being eroded - brown was one of the worst converting colors, and now both of the new universal color converts so far use brown, but it can’t be looped with just converters either. So maybe we are headed in that direction where there are converter loops for every color and by then there will be room for are empowered converters, however…
Keep in mind that everything added after Mercy was colored by mercy, and adding a Mercy-like and a Fox-like is bound to create a new, super obnoxious meta that will be even harder to shake. Mercy sort of dropped off with all the power creep, even if the does a totally unique thing that gives you a “free win” like 20% of the time. If we had one for every color, I have a feeling they really would be “too good not to use” especially since they’d probably have an even higher magnitude secondary effect than cleanse all and life gain, including damaging effects. Imagine having two empowered converters that could feed each other and a team. How do you stop both of them from getting a foothold consistently?
My top 10
My “most used” troop is still Mercy despite rarely using her nowadays because of the thousand and thousands of battles I played with her when she was basically the best fast start option by far, and also was (actually kind of still is) the best counter to an enemy Mercy, which was really dominant for a long time. Going into the Unity port, she had probably about 4000+ battles out of the 10,000 or so battles I had on the account. Compared to this, my kraken had in the double digits before Unity went live and accrued over 4000 uses (2000 battles with 2) during the period I could “tentacle bomb” entire teams to death. Valk is from pre-unity, mostly with Mercy, Ragnagord after unity port. Infernus obviously after, since he came right after the port. Krystenax mostly half and half. And if you are wondering why Carnex, Bombot and Rowanne are on there, that and a Mechanist with prismatic orb comprised my fastest possible PvP team for a while until skill bonuses pushed too many setups out of 2-3 shot range and defense teams got too “fast” for me to take them out before they could retaliate.
As it stands now, I mostly trend toward directionless spell spam because it is faster and still safe enough to win (hence, Infernus and Ragnagord seeing an upward trend). At my current rate of play with the teams I normally use, Mercy will be usurped from her spot in a few months.
Plus, as others have pointed out, Mercy was rarely seen on defense recently until until Ishbaala rolled out. If there is anything to blame for a Mercy resurgence, it is Ishbaala and Diviner. Aside from this, she also isn’t even in my consistently fastest setups.
tl;dr: Mercy is good and unique, but adding mercy-likes for other colors will probably have more than a few unforseen consequences. As it stands now she is not on even generally used in most my consistently fastest setups (except with the completely new synergy of “fast divines”, which was a bad idea in an of itself, which has potential to overtake my current fastest setups when facing not-fox teams and is by far my fastest and safest setup on my alt account at this point because opening with an exploder is risky with low stats). Other supports and other things that use her color combo or fit one or more of her roles are perfectly viable (but some aren’t, but that can be said about most troops that are meta-viable in any way). 9 months to a year ago, I would have considered her completely dominant for her each of the roles she fills, but not now.
tl;tldr: We finally got the a point where she isn’t completely dominant or even really seen outside of fast divines or the two people using a maw setup, so it would be a bad idea to open that can of worms again.