One of the problems with the concept of this is that a lot of the best heroes are all arounders that either have poor synergy and/or don’t excel in teams (Lianna is great and all but only truly shines in combos, like with Evelyn). In theory a rainbow 5* elite squad might be Drake-Hel-Athena-Lianna-Gravemaker (organized in descending color), but that sounds like a bit of a questionable team on defense and somewhat laughable on offense (does anybody go full rainbow anymore)?
Also that sounds bad on Titans and risky in events/rare quests due to the lack of healers.
I mean a list of great heroes is great and all, but without any team synergy, it doesn’t mean much. Delilah-Kunchen-Ariel-Alberich-Ares are great heroes too, but that sounds like an awful team in pretty much everything.