The easiest way to beat her is to Kite her around the room. Just keep moving in a circle away from the spheres, and they don't hit her, so she does not heal.
In case you don't know... kite is when you force the enemy to follow you around the area.
I beat her last night with a level 9 nightblade in 3rd person view. I kept her confined to her starting point, killed her 1st summon, use my stamina for blocking/stunning instead of attacks, and when she was stunned killed her orbs. Before I went in I drank some stuff for stamina regen, made sure I had 5 healing potions ready in my quick slot (only used 1), and made sure all my gear was close to my level, repaired, and that the enchantments were fully charged.
I beat her when i was lvl 9 nightblade. I did find it difficult to hit the healing orbs at first, which drew the fight out a lot. But what i finilly did was us tab targeting to target the orbs. Because before i started doing that for some reason i wouldn't hit the orbs almost no matter what.
Also like stated kiting is the best way to do this. I beat her with my 2 hand sword. Didn't stop moving once.
P.S: I'm doing this on my phone sorry for the format and spelling errors.
Grab the 'Silver bolts' skill from the FG line. With that as a knock down and "Strife/FunnelHealth" plus "Teleport Strike" using a bow to hit her from distance - she neve got off the ground while I killed her at level 9.
I understand you wanting to play the game in 1st person view for immersion. But doing so puts you at a huge disadvantage in this game do to way less situational awareness.
I'd suggest trying to learn the third person play style.
I still zoom into 1st person occasionally if I come across some amazing scenery, but other than that it's third person all the way.
Good luck with the fight. Destroy those orbs with very simple light attacks. Keep strafing to avoid her ground spell that dazes you. Keep up strife/health funnel at all times. And only Block her heavy attacks then quickly follow up with a heavy attack of your own.
I didn't think my hangover was that bad this morning until I spent 10 minutes trying to log into my old Etch-A-Sketch
I did her on a Bosmer, Bow-weilding Nightblade. Used Syphon DoT/Heal to keep myself healthy and kited her away from the orbs while using the Bow skill AoE to take them out. The first time I tried her was at level 7 and didn't know the mechanic. At 9, it was fairly simple and quick.
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The only zone I have tried in is Ebonheart Pact and last time I tried the orbs followed Dosh off the platform; so kiting would not work. Also no matter how much damage I did - a single sphere would heal her completely.
I generally have trouble targeting anything quickly in 3rd person - tabbing around seems too slow. On other fights I have noticed swinging happily but suddenly targeting nothing. I would rather use 3rd person but targeting is plain broken for me; 1st person I can at least hit something.
Finally did it with a bow in the AD and using "Silver bolts" - but I think I got a lucky at some point because she like went from 60% to 10% like very quickly.
Forgot to mention I have get to try the EP version which was the initial problem area; the orbs spawn much closer to Doishira there.