Loved this battle. But actually, on normal difficulty it is already doable at level 6 without any special allies. At least, I did yesterday. I had my 8 castle guards though, but nothing fancy there.
Just use crowd managing spells and kill the lordling first.
My party:
Me (Fighter/melee using stances for tanking)
Eder (Fighter/melee using stances for tanking)
Aloth (Wizard/ranged unique soulbound scepter after spamming confusion)
Durance (Priest/ranged using all buffing spells for fighters; started buffing my npc army)
Kana (Chanter/ranged spamming wyrms)
Grieving Mother (Cipher/ranged spamming silent scream, pain block and that domination spell)
Especially Silent Scream rocked for taking out those huddled groups of enemies as I learned late in the battle. I only had Aloth ko-ed, which I guess could have been avoided if I had learned about the effectiveness of that cipher power sooner.
Same for the Eternal Paths... I see people complaining on Reddit they cannot fight the Drake at level 6.... I am on the 7th layer of the paths and was doing fine at level 7. Just use hit and run tactics and buffs, guys...