Actually, I think Arcana's comment about incompetence was meant to imply that it was incompetent because it happened by accident, rather than via design. If the devs had designed all the ATs to solo deliberately, it would have been good design. But since the devs wanted Controllers to be a teaming AT, then having Fire/Kins soloing the way they did, was poor design.
Their design was that Scrappers were to be used for soloing, and everyone else should have problems. And Tankers and Controllers should be desired on teams (but more than 1-2 usually was not that desirable). Since things didn't turn out as they wanted, they clearly did not achieve what they wanted.
That what they got instead turned out to be good is more of a happy accident than competent design.
Exactly so. As deep into the game as I4 the devs were still designing around archetypes as if they had far more fixed roles on teams than the players felt they should, and were still thinking in terms that trinity-style gameplay could still be salvaged. The "everyone should be able to solo" informal design rule didn't really become a genuine design rule as far as I know until CoV. Look at CoV archetypes, and notice the shift in design. CoV is obviously "post-trinity."
But if the devs actually had a strong grasp of how to make the numbers do what they wanted, we would have never gotten the City of Heroes we ended up with. To put it in direct terms, the devs did not have enough control over the numbers to fine-tune archetype power between "lame" and "overpowered" so most things ended up overpowered relative to the design. At launch, powerset combination meant more to your overall power than archetype. Invuln/SS tanker? Godzilla. MA/DA scrapper? Doormat. Dark defender? Awesome. Electric/Fire Blaster? Roadkill. Emp/Electric defender? Useless except as a sidekick. By the time they figured out how to fix it, it was too late to fix: City of Heroes became the best MMO in the history of MMOs to solo in, because the devs handed out powerlevels most admins don't have in other MMOs. They couldn't bring down the overpowered stuff to "correct" levels except in the extreme cases, so they were forced to buff the players upward to balance archetypes out. Players always complained about nerfs, but the history of City of Heroes is an 80/20 buff to nerf empower-o-rama.
Incidentally, the last vestige of trinity-thinking lasted surprisingly long. It was the legacy of Blasters having no alternate design ethic once trinity was no longer the law of the land. In my opinion, it wasn't until Arbiter Hawk started to look at Blasters - literally in I23 - that I think Blasters escaped trinity-thinking; the last archetype to do so. Also, just a bit too late because I24 would have been the first issue to contain the start of non-trinity Blasters (one of my regrets was that I think in AH I finally had a Blaster ally on the dev team that thought about them somewhat like I did, and was willing to experiment with them outside the glass-cannon trinity model, and I'll never know where we could have eventually gotten Blasters to).
In any case, none of this was even remotely by design. It was 100% accident.