This may be too late if you already got your answers to your questions but if not, then I have found Medusa is very easily done solo with a sampy. I use a bladed staff for armor ignore. I armor ignore her till my mana gets too low then I switch to lightning strike.
Absolutely DO NOT disarm her. I made this misstake when using a guardian axe and barely made it out.
If you don't know this already Medusa can be skinned for scales while you are fighting her. Her scales are used to make gargon lenses which prevent her from turning you to stone and making doubles of your character. (you also get her scales after she dies but these don't work as well).
In order to make the lenses you will also need the crystals farmed from the first demon room of Prism of Light (the white crystals with the timers). With a alchemist (use a good tali) you turn the crystals into crstal dust (first page of the alchy menu, last option) It takes 4 crystals to make one dust. Once you have all the dust you want to make you will need to jump on your tinkerer. You will need three crystal dust and 2 Medusa scales to make one gargon lense. The lenses will have different amounts of charges on them (somewhere between 28-35)
The lenses can be applied to your headpiece, gorget/mempo, earrings, and shield if you carry one. I always use one lense for each one of those armor pieces so if it misses on one it will hit on the other.
Hope this helps!
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