DnD Warlord
Adventurer
Well in the 15 ish years since our games have gotten better and more fun not worse and I have never seen anyone do what you said it is a recipe for...That sounds like a recipe for one hellacious round of arguments, to the point where the game would quite likely collapse before it began.
It's also ripe for one player in effect being able to determine what everyone else plays, by (without actually saying it) vetoing everything that doesn't fit with his vision of what those other players should play. For example, if this player thinks Mary always plays Wizards well he might decide to veto everything Mary puts forward until and unless it's a Wizard; ditto Bob and support-style Clerics and Joanne and Bards/Rogues.
Why?
To be blunt about it, this sounds a little on the selfish side: just because you've decided to play a front-line tank doesn't (and IMO shouldn't) give you a monopoly on front-line tanking, yet that seems to be what you're asking for here.
That, and from what I can tell the 'role' aspect in 5e isn't nearly as front-and-center as in 4e; in 5e parties where roles are over- or under-represented are much more viable.
As for why it goes back to the 3e days. We had some power gamers who ruined the game for us. The one in question this time played a cleric who would throw buffs on himself then run into combat... then when the fighter died (since no healing and he had both less buffed AC and HP then the cleric) it caused hard feelings.
I see nothing wrong with 2 characters working togather to fulfil a role. But only if both agree to it. If I am sitting down to a table (well a virtual one right now) and there are 5 or less players I expect us to each bring DIFFERENT things to the table not the same.