Stay away from these unless you are doing the task "Yrelia #1: The Great Hunt" to use the Bixie Fire Blower on them once they reach 10%. Otherwise, you will not be able to kill them without it.
This mob will go down to 10% HP and will not die. Avoid at all cost. If you have a chanter, bard or other class that can erase aggro then you can end the fight. Otherwise, it will follow you till the end.