Player's Handbook said:
Controller (Wizard)
Controllers deal with large numbers of enemies at the same time. They favour offence over defence, using powers that deal damage to multiple foes at once, as well as subtler powers that weaken, confuse, or delay their foes.
(My emphasis)
The changes to zones that operate to reduce area damage to mass targets reduces control, by WoTC's very own inital definition of the role. EOT damage reduces control. If you choose to define "control" as "making enemies think about battlefield postioning", EOT damage
may affect control - but reducing the damage from the zone
as well (e.g. Stinking Cloud) just adds insult to injury.
Flaming Sphere has a range 10. It must always remain within 10 squares of its creator, who must also continually retain line of effect, and must have line of sight to move or sustain it. It is party-unfriendly. That is is largely more effective than any other 1st-level daily wizard spell merely reflects the general suckage of other 1st-level daily wizard spells. I have never seen Flaming Sphere break an encounter. I have seen it alter the flow of battle, particularly in confined spaces. I have also seen - from both sides of the screen - the conjuring wizard receive the almighty smackdown from every unmarked enemy on the battlefield as soon he or she rolls it rolls out, the best defence from a dangerous zone being to knock its creator unconscious.
The changes to the wizard (sorry, arcanist - ugh) that are proposed are to address (1) a systemic flaw with damage-on-entry zones; and (2) one-trick ponies and damage optimisers.
Problem (1) requires a system-wide fix that should have occurred years ago. Zone damage 1/turn appears to be the most widely adopted house rule ever. Problem (2) is a problem for organised play, not for home games (or at least well-managed home games). I will continue to use the PHB wizard in my own games, thanks.
Cheers, Al'Kelhar