I was told quite frequently, and even had seen evidence of, that stamina actually made people play very poorly in many aspects. They'd use stamina as an excuse for example to try and use area-effect attacks as single target attacks or generally not hit more then one enemy with any AoE, not even making any effort to line up the cones. They took stamina so they could, quoting one of the guys that got me into city of heroes "Spammedy spam spam". Thing is, spamming is ALWAYS a bad tactic, universally. Spamming in the tactical sense means "Spraying and praying", not aiming, not timing powers or using them to support each other, not picking the threatening targets, just target a guy and attack with everything you have even if it's not held by a controller/tanker, even unbuffed and even if it's a +4 boss and your build up/aim is down.
Generally, being an idiot and relying on luck is what spam truely and always has been in all games. I didn't take stamina most of the time but instead hit where I knew hit the hardest and helped the team most as a blaster. Things around me died in a precise manner, I also did not need stamina as I had endurance management powers like power sink. Only time I took stamina was if I had a brutally punishing powerset like storm summoning and even then I always made sure I took another set with a lot of skippable abilities. If I had a powerset combo that was both to expensive to use endurance wise, no built in endurance powers and skipping more then 3 powers to take stamina gimped it? I didn't do that combo.
Powersets I could think of that half-depended or depended on stamina:
Storm summoning(hurricane, freezing rain, snow storm and thunderstorm were both used often AND cost a ton of enduance).
Sonic resonance: (far more endurance-intensive powers than force fields plus having to aat the time renew everyones shield took half an end bar in a 8 man team)
Maybe martial arts(But I never touched this set, no AoE = no taking from me, I hate having only single-target most the game).
Time manipulation: Lots of expensive powers that costed a brutal amount and a very poor-quality endurance management power, even with stamina I had a hell of a time keeping up with this sets power demands.
Other sets though using that much endurance were few and far between. Stamina wasn't that necessary, but I felt everyone always taking it as a must have requirement for EVERYTHING were actually pretty bad at power use. Especially if they took it on powersets with things like quick recovery, and I then found people who felt both cardiac AND ageless incarnate powers both were must-haves, to, which was bullcrap because Ageless by ITSELF could handle even the most expensive builds at tier 3 or 4. Having at least 100% endurance 75-100% of the time was more than enough, let alone also having a full end bar on cast plus 800% recovery for 30 seconds and then 300% extra for the next 30 seconds after.
You use far more endurance if you were using the wrong powers all the time, ultimately. Fireball on that archvillain seem ok? Use flairs instead, cheaper, especially when they buffed it's animation speeds, it cost only a THIRD the endurance, cast fast with the animation buff AND did the same damage. Energy torrent on weakened lone guy? Again, power bolt, seriously. Freezing rain on lone guy thats weakened? Oh I saw that once or twice. Spamming powers just made you use about 2-3 times the endurance you needed to, i'm not kidding there and I saw so many spammers know?
I had nothing against inherent fitness, mind you, since a few builds I found here and there did need stamina, but there were quite a few more that honestly I felt didn't if you actually used your powers correctly rather than spam.