Of course group dynamics have gone the way of the dodo bird since original launch. The game has changed so much since then I'd be more astounded if they were able to keep that same dynamic for over 11 years.

And to be blunt, most people wouldn't stick around if the game didn't change and adapt. Getting the same boss fights instance after instance would be boring and tedious. Quite frankly, most people don't stick around anyway, and that's something that the devs had to take into account. Most people play a game - on average - for 3-6 months and then they move on. For in-depth games like this one, you might be able to stretch that a few years. But still, there aren't that many people (percentage-wise) who have remained in game for 11 years and counting.

But more to the OP's point, I can remember plenty of times in the early days of SoA where you couldn't just slap 6 any-classes in a group and expect to survive. You ALWAYS needed 1 tank, 1 heals, and 4 dps. That's just the way it worked back then, and still does, for the most part. The DPS classes could change, but there was only 1 guard and 1 mini in any given group. Plenty of times where I saw "CD 5/6 need tank" in chat back then.

I'll also point out that the real problem with most boss fights nowadays (and someone already mentioned this) isn't that the mechanics are just a DPS race. It's that DPS rates have gotten to stupid points and a DPS zerg is generally all that's needed to get a boss down. Then the mechanics won't show up anyway. This leads to the point where truly any 3 toons can run CoS on T1/T2 and get thru it without much thought. And most 3mans are that way. Heck, a lot of 6 mans are that way.

To me, the really disappointing thing about the game is that all the classes are tending to blend together, where there's no real differentiation between the DPS classes (or mini's really). Guards can still have trouble generating lots of DPS, but even in red line, that's not much of an issue anymore either (they'll never be RKs, but RKs will never be tanks either). Unfortunately, it didn't take long after SoA for "class balancing" become a euphemism for erasing the lines that made classes distinctive.