Just as a note - I definitely recognize some groups used the power and had no issues with it, and everyone does have different viewpoints. For our group, it was definitely in need of fixing. Like others have mentioned, I've seen folks chastised at LFR for not having it, Stinking Cloud, and other similar potent auto-damage attacks.
Any power that gives out free bonus attacks is stronger. One that did so throughout a combat, without rolling to hit, against multiple enemies? Even with the limiting factors, it was pretty darn potent.
You want to change Flaming Sphere to EoT? Fine. That's a perfectly viable choice. But the power, as it is written now, is simply not viable.
I agree it could use a bit more tweaking - I think that is very different from not even being
viable.
To compare it with other powers:
Sleep: Apples and Oranges, really. Sleep is a non-damaging power that can either shut-down an encounter or accomplish almost nothing. Those whose builds tended towards such things would prefer it over Flaming Sphere both before and after the change - the two accomplish very, very different things.
Arcane Whirlwind: Good initial damage in a decent sized burst, and ok positioning control. Less useful for the previously mentioned 'bad choices' control. Being able to slide 1 enemy up to two squares, on your own turn, is very different from discouraging an enemy from approaching a ranged attacker, or encouraging an enemy to provoke opportunity attacks, etc. Arcane Whirlwind's initial effect is much, much stronger than flaming sphere. It's ongoing effect is much, much weaker - even compared to the new version.
Phantom Chasm: Another very good power. Again, a solid burst damage up-front, and enemies only. Good initial control (prone/immobilized) and it makes an area largely off-limits for enemies for the encounter. But that area doesn't move, which is definitely a big difference. Against the right enemies - where you can stay in that safe zone and force enemies to come to you - it works just fine. Against others, the ongoing effect will largely be irrelevant.
Fountain of Flame: Pretty much the same thing as Phantom Chasm, except it focuses on damage over control effects. Again, good up-front damage, a good zone effect, but lack of mobility makes it distinct from Flaming Sphere.
Overall, I find the new Flaming Sphere to remain a viable choice. The other powers mentioned tend to be better for immediate damage to a cluster of enemies, but have less potent effects over the course of battle. Flaming Sphere provides more use over the course of the encounter.
And that is really where daily powers
should be. Some will be the best option for one encounter, while others will be ideal for a different fight. Rather than one choice remaining optimum for both circumstances - which Flaming Sphere was, previously, where it did more AoE damage than all of the good AoE spells, and was more useful over the course of the entire battle.
I also disagree with the premise that Flaming Sphere doing a lot of auto-damage is some sort of grevious violation of the Controller contract.
I think you are confusing two seperate points of argument. A class having powers that let them work out of role is fine (within reason). Wizards having a high damage power isn't a bad thing. The problem was that high damage, inflicted automatically, to multiple opponents, over every round of the entire combat? Wasn't especially balanced for anyone. Just like its cool for rangers to be strikers that deal lots of damage via multiple attacks, but that doesn't mean an infinite attack blade cascade is still balanced.
In addition to this, folks have mentioned that they find the solution nice because it emphasizes the wizard's role. For myself, I would also have been fine with a solution that kept Flaming Sphere as a damage-based power but simply toned down the damage to a more reasonable level.
Instead, they shifted it to work more like the Wizard normally works, and I'm fine with that two. But I don't think the power was fixed solely because Wizards shouldn't do damage. It was fixed because the amount of damage it did was potentially unbalanced.
Otherwise, why is the Fighter's (a Defender's) very Striker-like Rain of Steel intact?
I'll be honest - I've long felt Rain of Steel is an issue for much the same reasons., and remain hopeful it will one day be fixed as well.
My point is, changing this power didn't "bring it in line" with other powers. All it does is ensure that for those groups that "always' saw FS being used will now "always' see Sleep being used.
Seems unlikely, given how different those spells are. I'm sure some folks will switch to different options. I suspect others will still use Flaming Sphere - as I noted above, there are plenty of situations where it remains a viable choice, and we still really don't have any dailies that provide a similar ongoing effect throughout the entire encounter. The ones you offer as comparison tend to either lacking the ability to be moved (Phantom Chasm, Fountain of Flame) or have a very minor effect (Arcane Whirlwind, with a 2-square slide for a single enemy - or potentially two enemies if you don't need to move the zone, or are willing to give up your standard action.)