It’s pretty easy to tell that the original idea behind Overwatch’s team compositions weren’t going to include or balance around the idea of two or more tanks. Even now, most Tanks can produce a lethal amount of damage to individual targets and seem balanced around the idea of withstanding damage from multiple sources (up to a certain point).
The recent changes towards barriers further exemplifies this issue of how much effort is necessary to eliminate a single tank and the rise and dominance of the GOATS meta drives home the idea that Blizzard never really considered the possibility of multiple tanks being a stable or viable team composition.
While I don’t think the idea is too outlandish, I don’t think it’s viable either, not without reverting some changes delivered to barriers among other minor changes.
Even, I’m not sure I would agree with the idea.