score:3
Most likely this is Areopolis, or modern day Rabba.
This rendering of the word seems indeed strange enough for editors to explain their choice of transcription after noting that the very sect Osseans itself is a unique reporting from Epiphanius to begin with as follows:
Ἀριηλίτιδος ist nicht zu beanstanden; der Name der Landschaft ist von Ἀριὴλ = Ἀρεόπολις vgl. Eusebius Onomasticon S. 36, 24ff
To be honest, my nerves get allergies from the user interface on the above site, so I did not check on the exact edition mentioned there. (Neither source of the digitisation nor the reference of Eusebius mentioned. Anyone able to stomach such UIs & willing to help out: please do so.)
One version of Eusebius' Onomasticon matching the German/Greek text above reads:
Arina (Isa. 15:9), also Ariel. A, S: the lion of God. This is said to be Areopolis because from that time even up to the present those who live in Areopolis call their idol Ariel, from the worship of Ares, after whom they named the city.
— Translated By G.S.P. Freeman-Grenville, Indexed by Rupert L.Chapman III, Edited and Introduced by Joan E. Taylor: "The Onomasticon By Eusebius Of Caesarea", Palestine in the Fourth Century A.D., Carta: Jerusalem, 2003.
For comparison:
Epiphanius, writing in the fourth century CE (c. 378), tells us of a figure named “Elxais,” or “Elchasai,” who led an offshoot of Jews called Ossaeans that were “of those that came before [Elxai’s] time and during it.” The Ossaeans “originally came from Nabataea, Ituraea, Moabitis and Arielis, the lands beyond the basin of what sacred scripture called the Salt Sea,” in Arabia, the Hijāz.
— Micah B.D.C. Naziri: "What The Religions Named In The Qur'an Can Tell Us About The Earliest Understanding of 'Islam'", Wright State University CORE Scholar Thesis, 2012. link
Regardless of the strange listing beginning with Nabatea, Moabitis, Iturea (which on first glance looks like a clerical error for Idumea to me, although that looks plausible in English, but less so in Greek, Hebrew or Aramean …), taking the ancient source at face value, and arriving at an Areopolis in roughly that area, we now look on modern day Rabba in Jordan.
One caveat to observe: Rabba/Areopolis or Rabbat-Moab might be identical to the more ancient but not precisely locatable 'city' of Ar/Ar-Moab (as known from Isaiah 15:1), but like Ar also Areopolis seems to be mentioned often in older texts not necessarily as to mean 'a city', but also 'a region' of that name.