Matchmaking without the Trinity: how would you do it?

[Zojha]

I would disagree that it is as simple as you are making it out to be.

On that, we will have to agree to disagree, because IMO, it really is that simple "on principle" and yes, mechanics can be just as complex and difficult. You can have the same effect you're describing with the MP supply by simply having a damage reduction song instead. It's the same on principle. The mana song supplies the healers with mana and those in turn convert it into HP for the party. A damage reduction song would reduce the damage the boss does and thus increase the effective HP of the party. It doesn't matter because it's interchangeable, as it all fulfills the same purpose - increasing the effective HP of the party so that the boss needs to do more damage to deplete it. On the meta level, the game is only about health and damage - whoever depletes the others HP pool via damage first wins.
Although I admit with how powerful healing is in this game, you'd have to make substitutes completely ridiculous to achieve the same effect - it's just that strong. I'd also note that the positioning would be the same in either case - it would just be the currently aggro'd player doing the positioning (whoever that would be), rather than the dedicated tank.

Have you played Guild Wars 2?

Yes, though only for a fairly brief while after hitting the level cap due to horizontal progression boring me to no ends. And I found that the encounters weren't very well designed for the combat system they had. That's why I bring up a mechanic heavy fight like A11 - I didn't find anything of the kind in GW2. Instead, I found simple bosses that had strong unavoidable autoattacks that I had to kite endlessly. Most of the mechanic indicators were very vague, if existent at all. And all of it coupled with a much lower rotational complexity.

Yes, I agree - it was dull. But I disagree on the reasons as to why it was. Content doesn't need to be simple to work without the trinity - it just can't have lots of unavoidable damage. The epitome of trinity combat design is tank and spank, the epitome of trinity-less design is bullet hell.