Nyarlathotep - has a A-frame -15% atk debuff that can also give a small % rage gauge reduction (and give a random ally an atk buff)
has a A-frame -15% def debuff that can also give a stun extension debuff (and give a random ally a def buff)
and can poison an enemy (up to 7500 turn)
Her main selling point are the atk and def debuffs. The rage gauge reduction and stun extension are bonuses. The random ally buffs are not relevant at all. The poison's whatever; won't even notice it at higher atk.

If you have one of Satan (matches the A-frame def debuff and will surpass it after awakening) or Hades (her A-frame atk debuff ends up stronger), Nyarlathotep loses practically half of her value. If you have both, just pass on Nyarlathotep. If you have neither, Nyarlathotep actually is a pretty good SR.

Agni - her main thing is having a +15% fire buff. Not a bad SR, but can be pushed out. Need more info on what other fire kamihime you have.

Konohana Sakuya - has a B-frame -20% atk/def debuff. The 500 HP/5 turn party heal is a nice bonus for R tier. See that debuff? It takes Amaterasu to definitely push her out of the roster. If you don't have Amaterasu, that debuff alone is a pretty strong argument to fit her in your fire team.

As far as other notable R's...
Zephyrus is actually really hard to get pushed out of wind teams by the current SRs.
Nergal & Baphomet can be used in a R/SR fire team for a while due to their A-frame 10% debuffs.