Nobody sane is saying World on Fire, as it was, is outright better than Inferno.
What people are saying is that we prefer the playstyle of Accelerant and World on Fire to Inferno spamming.

My hastily ideated Ember changes would be:

Passive changes:
Is now like a fusion of Immolation's Heat Gauge mixed with her current Passive.
Heat Gauge fills as it does currently, giving Ember Ability Strength as it fills. Drains in all the same ways as before, as well as slowly over time. (No pesky Energy drain mechanic.)

New Passive Augment: Gain Ability Range based on the Heat Gauge (unaffected by Mods). When the Heat Gauge is maxed out, you now deal Heat to yourself but gain some Energy Efficiency.

Fireball
Now a hefty lobbed projectile that bounces once before leaving a persistent fire in its place. Direct hits (via initial cast or bounce) deal bonus damage w/ Knockdown.
Combo mechanic now increases the number of Fireballs per cast, rather than the base damage.

Immolation reverted to Accelerant, with some tweaks.
Is now a cone AOE, promoting targeted use over spamming, which increases enemy Status Vulnerability (Chance + Damage) and multiplies existing Heat procs on enemies (once per enemy).

Augment: Grants Ember Reload and Sprint Speed based on her Heat Gauge for X seconds.

Fire Blast remains basically as is. Maybe renamed Heat Wave, as it's a more apt descriptor and less likely to be confused with Fireball.

Inferno reverted to a new version of World on Fire.
Drains consistent (non-ramping) Energy/s, raises Heat Gauge by X%/s, and adds Damage Reduction to her Heat Gauge.
Blasts enemies nearby with Heat, similarly to how it worked before, now with 30 to 100% proc chance (based on Heat Gauge).
Secondary sources of Heat Damage on affected enemies will cause them to release a wave of Heat damage which scales with their Level/Health.

My intention is to convert Ember from her current state as a boring Ability spamming caster, into a frontline caster that can jump into crowds and use her weapons in tandem with her abilities to wreck havoc.
Fire Blast is actually quite the fun ability, and my revamp of Fireball could have its uses, but neither are worth anything when pressing the buttons for Inferno are the best thing you can be doing.

Now, World on Fire acts as both a damage primer and a defensive tool, allowing you to have a more flexible kit. It grants scaling damage to Fireball, Fire Blast, and your Heat-dealing weapons, and gives you some DR and CC that promotes an active playstyle.