ok, 2 arm doppio is decently op, and can beat most stands/specs. let's go over the moveset.
E and R (1st form) are low cooldown moves with 50 damage, i'll estimate it to be around 3-4 E/Rs before killing a person, you could combo with R and then E.
epitaph is of course, cancellable, allowing for sneak attacks, always press this just before you go into second form.
as for V, like epitaph, it allows sneak attacks for combos.
2nd form time.
E (barrage), good for chip damage, but easy to escape from, highly recommending you depend on other moves instead.
R is the best move when it comes to runners, as the hitbox of the scalpels is the same as TWOH's knives.
T is spoh H but you can grab people if it hits, allowing for combos, try to bait your opponent fast as this has a long cooldown
Y can be paired with T. does 50 damage but with long cooldown.