Super hella necropost.
Last night I solo'd sippoy with no difficulty. I had to get back at him for the mega wipe he caused my alli so long ago. I was helping a friend with drg seals and there he was, i was not set up properly but i thought id take a swing at him. I used razed ruins, sanguine scythe, and voracious violet for atmas, and used no Eva gear except for blithe mantle and Hermes feet. I was /nin with soulsoother. Deployed my automaton behind him while I proceeded to destroy him. I kept constant 2x dark and 1 light maneuver. He had a hard time getting through my shadows except after his aoes. Each -ga iv and Stygian would take me down to about 1k hp, which my automaton would immediately remedy. There were a couple close calls, in which I popped my lucid temp, as well as a stray role reversal. But other than that, a very smooth fight.
If you came with a better Atma set up, with some -mdt, Eva, and regen, you should have no problem making him dead.