Immolation meter: Please don't keep this mechanic. It's not needed and is going to be counter synergistic. It will FEEL BAD.
Fireblast: As a power it is still redundant, and the knock-back is hurtful to a Melee Ember, who now needs to go chase down enemies.
Combining Immolation meter and Fireblast, as you currently do, is again anti-synergistic and punishing to a melee style. You're making Melee Embers not only reduce their DR, but now they also have to go chase down the things they're trying to kill.
I've long advocated for the return of Overheat to Ember's kit. I've also long advocated for it to replace Fireblast (which has been a rather redundant power since Ember was added). I strongly encourage DE to consider the following:
1) Fireball (25)
This power is mostly fine. The fixes to animation and timing will help it. Perhaps reduce the charge time, or truly make it a scalar (uncharged x1.0 to full charge x2.0, with the options of x1.1, x1.35 etc). A Scalar will also be useful for a Fireblast as a power combo effect.
2) Accelerant (as a grenade power) (50)
There are many good reasons to keep most of Accelerant around, and to convert into a grenade. Being able to throw down a zone with a Slowing and Debuff effect gives Ember a soft CC option.
Combo power with Fireball + Accelerant zone = Fireblast effect (scaling from Fireball charge level).
Combo power with Inferno. Enemies stepping into Accelerant patch ignites it (no Fireblast) and makes it a carrier for the Inferno DoT, spreading to enemies that touch the new Inferno zone.
Accelerant remains the Damage booster power and you don't need the "Immolation meter" for that effect.
3) Overheat (or if you must "Immolation") (6 per second*)
Drain-over-Time power. Cost 6 per second
Reduce cost based on # of On Fire Enemies (already being tracked by passive), scale from 6 down to 3.
DR% based on power strength (thus partly based on passive), or directly link base DR to # of On Fire Enemies. Either way, you don't need a separate Meter for this.
Combo power with Inferno, Ember can become a carrier for Inferno DoT, by running into an Inferno'd enemy (or burning Accelerant zone).
Double Drain-over-Time cost (12 max to 6 min, scaled).
Roll to self-cleanse early (stop, drop, and roll).
There really isn't a good reason for the "Immolation meter," it's just another thing to track. Ember's should only really need to track:
Number of On Fire Enemies
By making Overheat a Drain power, and having its cost subject to the number of On Fire enemies, you reinforce the two things Embers should be tracking. If you're just running around with DR on, its going to drain you out fast. But keeping the drain low also means needing to stay on top of keeping enemies on fire. If everything is dying within fractions of a second, Overheat will stay costly to keep active. The "Immolation meter" could just be an abstracted UI indicator of the number of On Fire enemies.
Allowing Ember to pickup the Inferno DoT and be a carrier, while Overheat is active, allows players to have the "weeeeeeeeeeeee I'm running around and everything is on fire" fun at lower levels. But with a bit more work, as they have to make physical contact with enemies, or can further combo off Accelerant by dropping a zone on their feet (turning it into an Inferno zone). Yes, the doubled cost will start to drop as the Ember sets things on fire, but it won't be as sustainable or easy to nuke the low-level-world as the current World on Fire does. And that cost won't stay low if things die off fast. Again "Warframe Energy" + "Enemies On Fire" management. If that seems too good, make it the Augment.
4) Inferno (100)
Great change, but see keeping Accelerant as a way to expanding the options for keeping the "World on Fire" and spreading, especially when the AI has pathing problems. That way Embers who want to 'passively' DoT the world to death can a bit more actively toss Accelerants around.
You do not need Immolation Meter to increase damage, you've already got that being handled by Ember's new passive. Just make sure the special Inferno DoT hooks into the # of On Fire enemies count, you're already tracking.
Passive) Ability strength for # of On Fire enemies
Good change, the more that's on fire the more painful the Fire gets. Just have it apply to Inferno DoT damage as well, and you don't need an "Immolation Meter".
Combo Effect Fireblast:
By making Fireblast a combo effect instead of a power, you give Embers the OPTION of that hard CC knockback if they want it. And where they want it, instead of just on their feet. Including being able to "blast" enemies toward them, or into other teammates traps. It also gives Embers a reason to keep using Fireball and not just ignore it in favor of an Efficiency Inferno. Working off the Charge Level (scalar) of Fireball would also give an Ember control over the "force" of the blast. An uncharged Fireblast could have negligible knock-back, good for an AoE fire proc. A full charge, could do the major area clear rag-dolling. Options, choices. A quick 2+1, at her feet, and its 75 cost Fireblast as it currently exists. A slower 2 + charged 1 , and you have a 100 cost "everyone away, and be on fire" zone clear.
Overall setting up Ember's kit this way, you can allow different play styles to Ember that don't punish her for doing them.
Everything Burns (power & weapon status spam) is what we have now in the Mid to Late game, but won't allow Overheat to stay active for long periods. Especially on the Power Spam end of things as Overheat (as drain) will fight for Energy needs, on costly combos.
Face Melting Melee with Overheat and carrying an Inferno DoT, which isn't blocked by needing to Fireblast every so often. Keeping DR up by staying on top of enemies and keeping them lit.
Blasted Goal Tender, Accelerant zoning + Fireball (for a Fireblast) lets Ember clear Defense points and terminals (Interception hack points), without having to constantly stand on those points.
Smoldering Friendship, with Augments for Accelerant and Fireball, now your friends can play with fire too. And it only gets hotter as they do (spreading more fire procs, and raising power strength).
And she's doing it all in a "yep that's a lot of fire" way.