This is an unmissable story mission. I have copied the stages from https://gamewith.net/anthem/article/show/7923
I completed this mission on Pilot Level 7 and Ranger Power 60.
The Ursix doesn't come alone but the enemies it comes with(on normal difficulty) are only red bar Scars. Personally I kept my distance. I would throw an Inferno Grenade at the Ursix, use a Seeker Missile and then focus my fire on the other enemies and repeat until my Ultimate was fully charged.
It will throw rocks at you but you can see them coming and they are easy to dodge. If you get too close he will do his melee attacks which do a lot of damage