Well this is definitely not ACT doing something weird, it’s the game itself.

I have spammed hundreds of Flowing Strikes on the training dummy to replicate this event and I have succeeded. This appears in the in-game combat log exactly the same -not just ACT. This is from my in-game log:

You start using Flowing Strike.
You successfully used Flowing Strike.
Your Flowing Strike hits (Normal) Anima-Sim: Nightmare for 433 physical damage.
Your Flowing Strike hits (Normal) Anima-Sim: Nightmare for 5427 physical damage.

This is from 1 Flowing Strike. As you can see there are 2x Flowing Stike entries.

If the damage is being split, the game is doing it not ACT.

BUT I don’t think it’s a split. Because my highest non-crit Flowing Strike was 5573 during this session. If we add the above entries together that would reach 5860 dmg and I never hit a 5600+ flowing strike in a single hit let alone 5873. In hundreds of tries.

Furthermore another proof that this is not a split is that the smaller amounts can crit independently of the main ability damage. Meaning: even though the actual ability does not crit, the “echo” can crit and vice-versa. For example:

Look at Tenetur’s log I shared above. Her Swallow Cuts are doing 7-8k dmg. And these “echo” hits are doing 800~ dmg each. But sometimes they do 1800 dmg. Meaning it crit.

Second example from my own log at the dummy:

0:00:46 Pantheist Flowing Strike physical Anima-Sim: Nightmare 1,454
0:00:46 Pantheist Flowing Strike physical Anima-Sim: Nightmare 5,492

My normal hit is 5492. The echo base dmg is around 450~. But when it crits it does 1.4-1.5k dmg.

Here is an example from when main dmg crits, but the echo doesn’t:

0:01:33 Pantheist Flowing Strike physical Anima-Sim: Nightmare 452
0:01:33 Pantheist Flowing Strike physical Anima-Sim: Nightmare 15,436

PS: It is also worth noting here that the “echo” damage is different for every ability and even more strangely different for every player it seems. Giving example from Epherian’s log above, the base damage of “Swallow Cut echoes” was in 1.1-1.2k range; while Tenetur’s “Swallow Cut echoes” was doing 650~ dmg. However Epherian’s normal Swallow Cuts were doing 8-9 k and Tenetur’s normal Swallow Cuts were 7-8k range. So it’s not even proportional to the main damage. Epherian was getting much more “echo” Swallow Cut damage compared to Tenetur. Likewise, Epherian’s Flowing Strike echoes were 1.7-1.9k while Tenetur’s Flowing Strike echoes was around 1k dmg. Again disproportional to their main ability damage. Because Epherian is doing only like 10% more main ability damage compared to Tenetur, but his “echo” hits did double compared to Tenetur.

SO if this is a bug it’s not a fair bug. Because it’s not even proportional to your damage. In this combat Epherian did 29k dps while Tenetur did 23k. When we look at the difference between their REAL ability damage the difference is only 10%. But this echo thing is causing a larger DPS gap between them. And remember that in that combat I got no echo damage whatsoever. So I was in even worse situation.