It is overpowered, but it's a Weimer creation, just like a significant slab of the Tactics battles, so don't beat yourself up too much about it!
Just on my burb in my previous post, I can't recall exactly, but you
may need to go invisible initially to avoid having Redspike and Bloodspear follow you across to the east side. Sorry - it's been about a year since I did this fight.
Well done on your other progress!