Not sure about Om'Euvhi's but there are Aw'Euvhi's in Al'Taieu saw one today when I tried the new Dimmesional Portals. It was near where the one from Mea puts you.
Ahh I see now. The Aw'Euvhi's are NMs needed to gain entry to Limbus.
To my knowledge there are no Euvhi mobs in Al'Taieu, nor are there Om'-level Euvhis anywhere else. Only in Hu'xzoi (Eo'euvhi and Euvhi-type pets) and Ru'Hmet (Aw'euvhi and Euvhi-type pets and NMs).