I actually stay in my full sharpshot Overdrive attachment set. I only change 1 thing. I swap, I think tension spring 3 for Strobe II for the lamia fight.
I have 53% pet -dt from gear alone. 12.5% from frame, 9% stout servant for total of 74.5% without any attachments. I swap in dt set if I need to.
Tanking a single lamia is so easy as far as damage goes, it doesn't really deserve a tank setup. I'm not competing w/ other dps to hold it, so I use just the 1 strobe. and I do Overdrive to make it faster.
The real challenge is dealing with the hate drop mechanics and enfeebles.
I like to Overdrive Freyja. or Skathi when Freyja dead. Depends on which one I'm on.
Both have some annoying enfeebles (terror, petrify, DOOM/petrify) which are really tedious if you drag out too long.
Its often worht it to me to reset 1 hour between fights on VD. Lamia are already slow for most ppl to get KI again, resetting 1-hour adds a few more minutes. but when you get 10800 per fight its worthwhile.