I?ll start this by saying that I am?a Feet Tenebria enthusiast. This analysis will be post buff (scheduled for the 20th of Feb) and I?ll try to explain where to use her and why. Please excuse my poor english, as I am not a native english speaker.
S1 : Attacks with an explosion of poison energy, with a 50% (Max. 70%) chance to inflict poison for 2 turns.?This skill cannot trigger a counterattack. Attacks two enemies when Endless Nightmare (S3) is on cooldown.
S2 : Cannot be targeted by single attacks. Attack and defense +10 each time an enemy is defeated. This effect can only stack up to 5 times (50%)
S3 : Single target, stunning for a turn, decrease combat readiness by 50% when the enemy is defeated by this attack. 20% bonus damage for every debuff on the target.
Abyss :?She is optimal in almost every floor, unless the boss is actively punishing poison. Her passive will be ramped up from the first wave, making her extremely tanky despite her low base hp. As long as your tank doesn?t die, she won?t either. Solid 10/10 choice, save from very specific floors
Queen?(normal Raid) : May one hit her with a good comp. Her passive will be maxed from the mobs long before you reach her. If you can?t one hit her, she will still do tremendous damage. Having an AoE on her S1 will allow her to bring the boss down really fast. 9/10 on this Boss.
Karkanis?(Hell Raid) : Her S1 being AoE will get him out of stealth. She won?t be counterattacked from her S1 post buff so you?re not punished for attacking him while debuffed. She won?t be targeted by the mobs so a single cleanse when they use their non-attack skill will suffice. She will however still take damage from the boss AoE, even though her +50% defense will help her survive. 9/10.
Arahakan?(Hell Raid) : Optimal choice. Her passive still get her +50% atk and def so she isn?t too affected by ?unable to be buffed?. Her AoE S1 nets her a fast clear of the mobs. 10/10.
W11 :?Can function like a normal DPS with a permanent 30% atk. Not an optimal choice but if you have her geared and molaed, she is perfectly viable. 7,5/10.
G11 :?Optimal for One shot comp. 10/10 in that case. For a normal run, see above.
B11 :?Optimal for One shot comp, 10/10 in that case. For a normal run, see above (AoE S1 will allow her to retain fairly good usefulness)
A11 :?Optimal for One shot comp, 10/10 in that case. Extremely solid choice in a normal run since her S1 is now an AoE. 9/10 otherwise.
Hall of Trials :?Mage or Poison weeks give her the MVP easily. Pair with Tama for maximum efficiency. Slightly more efficient on Kayron since his adds actually die.
You probably knew, she is extremely strong against team with little to no AoE. Her recent buff will make her severely more efficient against units like Charles, ML Ken, Violet, ML Zerato, and anything with a counter set or Elbris.
And with her damage effectively doubled after her S3, tanking her will become extremely hard.
I think she deserves nothing less than +15. For a general PvE usage, I?d max her S2 first. For PvP, probably her S3>S1>S2.
Kal?adra is the best possible pick for her, making her already high damage even more lethal. She has a two turns debuff on S1, which means you?re likely to benefit from your own poison blast.
Her self imprint is atk%, always good but not optimal.
You should absolutely pull ? and gear her if she is the next in line, which she likely is. She was already pretty strong but her buff catapults her in the realm of ML Ken and Arbiter Vildred. Her buff probably stems from the rampant counterattack meta, which is pretty hard to deal with sometimes. She counter?s the exact opposite comp compared to ML Ken : she?ll stomp single target comp and counterattack while being weak to cleave.
SSB can still ruin her day though, since her S2 is not a counter and will be (probably) triggered even with her S1.
That?s all I?ve got, thanks for listening and have a nice day.