I played 10 fights and wrote an F8 report for each.
Summary of the summary:
Four out of ten fights were impossible to win in my opinion.
Of the four victories three were heavily based on easy/lucky boss patterns (mostly summon + no AoE attack from boss).
Two losses (f9, f6) faced very difficult boss patterns with no drone to tank but would have varying chances at victory in more lucky fights.
Averaging out I would say only one of these deck has a very good chance at victory, two or three have a decent shot at victory, and two have a small chance for victory on a medium difficulty boss pattern.
Kashio is extremely swingy and extremely varying in total damage. Currently the fight is very luck dependant. Selection of boss attacks, availability of the drone summon, boss target selection with the drone, boss attack selection (AoE damage vs single attack) provide a very high margin for total damage taken.
Zero defense decks can get lucky with attacks, summons and targeting and take 20 damage total, while high defense decks can fail to block the escalating 30, 40 damage attacks each turn in an unlucky boss pattern.
The drone summon is IMO the by far most important factor. It can fail but it gives chances to otherwise terrible decks to still beat the boss due to potentially 4+ free turns.
Kashio's abilities from artifacts can provide huge synergy/anti synergy with the player deck. This probably is a good thing, especially if you actually know the deck you built over four days. Some extreme cases might have to be looked at.