So let's jump in shall we. This is coming from the perspective of a player who enjoys fun but ultimately "useful" frames in the game. Here we go. (TLDR summary at the bottom).
Embers Passive: I am not too sold on this tbh. 10 meter range is way too short but ultimately I just don't think it suits her new kit. If she had a roomclearing nuke I could see this working, like, put a bunch of enemies on fire and then unleash something devastating. But it doesn't seem like she has that (maybe her 2 or 4?).
Embers 1: Fireball is still very underwhelming. I just can't really see any scenario outside of while reloading, that I would use this ability. You have to aim at an enemy and press 1. Why not just shoot your weapon? It will most likely deal more damage.
Embers 2: Immolation fixes the biggest issue with Ember - she had no Damage Reduction or reliable Crowd Control. Now she has 50% DR, which will increase along side the immolation meter. I would imagine her DR being capped at 90% like most abilities. The question is if you would need to be at the edge of the meter (right before it "breaks" and drains all your energy) or it will be more forgiving. Either way, a minimum of 50% DR is of course really good. My biggest question here is why isn't this her passive? There is no energy drain, so it seems to me that once you activate it you will pretty much keep it on permanently. Energy is super easy to manage in Warframe, so I don't see a scenario where I wouldn't have energy for her 3 to "cool" the immolation meter. When the immolation meter breaks it's supposed to do big aoe damage and drain all your energy, which I personally find really interesting but it's gotta be some serious aoe damage for me to do it intentionally.
Embers 3: Fire Blast, not much to say here. It strips armor in an AOE, deals damage and seems to have a guaranteed heat proc. So this would actually synergize quite well with the passive if the passive had a longer range. It also seems to have a knockdown, so some light cc is always welcome. Depending on numbers though I imagine this will primarily be used to simply manage the immolation meter and not for the damage or armor stripping.
Embers 4: Official forums thead reads: "Upon casting Inferno, all enemies currently within sight are struck by a fiery comet, lighting each target ablaze in a personal ring of fire". This ability raises a lot of questions for me. If you go to the twitch video at 34:45 you will see Rebecca casting this ability a few times quite far from enemies and I think it only connects the last time she casts it, when the enemies are not in line of sight because of the pillar. Anyway, my main question is if it will hit every enemy in front of you within range. Lets pretend 30-50m range. So the enemies on your far left and far right are obviously not standing near eachother. So will it hit both groups? Or will it only have one hit zone? Is it only FOV or 180 degress in front of you? I really hope it will hit every enemy within range with a meteor regardless of where they are standing. I fear it will only be in one zone. That would simply make her too weak compared to other room clearing frames. Heck, even having it only hit "all enemies in front of her" seems a bit weak when you have frames like Equinox, Saryn and Volt who can clear entire rooms regardless of angle. Also, each target being ablaze in a ring of fire seems neat but think about it; Who will they spread this to? If it's only 1 zone that will be hit - very little spread. If it hits every enemy in front you, well, they are all ablaze, except maybe the enemies who are yet to spawn/run in.
TLDR Summary: I think there are some really good ideas here and honestly a lot is gonna come down to the numbers on her 4 (Range and damage) and whether or not there is any point to breaking the immolation meter from her 2. So I will not pass final judgement yet. I am a bit worried though that her damage will be too focused on smaller areas instead of the meta aoe.
Wishful thinking: Make Immolation (new 2) her passive and maybe let it activate automatically after a small cooldown when the immolation meter breaks. And make it worth it to break the meter from time to time, to have cool nuking moments.
Make her 1 exalted: Pressing Mouse1 repeatedly spams fireballs from both hands dealing great damage, draining energy per fireball and building immolation meter. Holding Mouse1 does a flamethrower like move.
New 2: It could be her old 2 Accelerant, a small aoe WoF or something completely new (If immolation becomes her passive).
Make sure her 4 has the right numbers behind it.
Those are my thoughts and wishes. What do you guys think about this and what was presented? 🙂