bunshin does multiply (with clones) the damage when apply to swordman c1-c3 skills and kunai only. but at the same time, it receives damage 80% as well as divided the evasion by number of clones.
generally, korean tested out the swordman c3 skills (with bunshin) and it is around 2k-3k per attack x 5 clones = 10k to 15k. anyway, if doing with skyliner attack, it is also approximate getting 10k damage with 3 hits. the conclusion, people prefer skyliner with full evasion than taking bunshin risks with swordman attack skills. bunshin has high cd (40s) after duration (20s) over while skyliner is there always with 0s cd.
simply to make this way example:
kunai without bunshin = 5 attacks
kunai with bunshin 5 clones = 25 attacks (worth, right?)
thrust (swordman c1) without bunshin = 1 attack
thrust (swordman c1) with bunshin 5 clones = 5 attacks (0s cd, not worth because slow and low attack)
bash (swordman c1) without bunshin = 1 attack
bash (swordman c1) with bunshin 5 clones = 5 attacks (6s cd, worth!)
pommel beat (swordman c2) with bunshin = 1 attack
pommel beat (swordman c2) with bunshin 5 clones = 5 attacks (14s cd, waste 1 circle for this? not worth)
double slash (swordman c3) without bunshin = 2 attacks
double slash (swordman c3) with bunshin 5 clones = 10 attacks (not really, wasted 2 circles and high cd for 3 times)
now if you get highlander c3, you get skyliner lv10 always there. so when your bunshin active always, use 0 cd thrust to hit but thrust attack is lower than skyliner lv10, so why bother???
for fancy, people go for swordman c3. but it doesn’t really feasible most of the time. swordman c3 doesn’t give any special benefits.