More or less related to this old report - but now with a more general focus
Other tests
have confirmed the results for Cadence, and show a similar behaviour for Phantasmal Blades. I tested it today with Arcaneweaver, and got the following distribution (out of 100 attacks)
31 (1) | 25 (2) | 16 (3) | 28 (4+)
The stated value is 33%, the result is more consistent with ~66% passthrough. Only 31 out of 100 shots affected only the first dummy, 28 of 100 passed through all 3 dummies. It is the same behaviour as seen for ranged Cadence and Phantasmal Blades - the real passthrough percentage is two times the stated value. There was also a similar issue as Sandspitters had 50% passthrough for RF (V1.1.9.X Discussion - Endgame Viability - #44 by XandeRoot), which was 100% in the game.
This however only seems to be valid for certain attacks skill, @Gaurhoth tested Plunderer’s Talisman proc, and there the stated 70% seems to be correct (well, at least not every shot had passthrough). DEE with Deception of Dreeg also seems to be different, as the number of 1 target hits was 59 out of 100 (the number of 4+ was however 18 out of 100 - not necessarily what to expect by 33% passthrough), but clearly different from Cadence / Arcanweaver with 33%.
Just highlighting this old issue, because I am curious if it will be addressed or if we can accept the current in game reality as final.