I think Bismark has an average higher drop rate compared to the 3 Tu'Lia VWNM but, probably, still lower than the Zi'tah T3 droprate?
To give an idea on Qilin I went 1/4000ish to see my first Coruscanti.
LS mate went 3/1000ish.
Just comparing drop rates isnt good enough. A good metric is estimated time to get a pulse.
For example, FFXIDB says Aytanri drops from Morta at a 0,17% rate, meaning you need around 600 kills to get a pulse weapon. Considering campaign where you dont need to cap any lights, a reasonable time between kills+chest clearing is 1 min. Then you could get a pulse after 10h farming.
Zitah can have higher drop, but the real rate is uuncertain. Depending how your fighting it (with a proper party killing fast or solo) you need to consider how long your fight takes and most important if youre doing efficiently with a party, how you guys will work the looting? Are you sure youre getting a pulse weapon from zitah even with higher drop rate but with longer fights and competiting with other players?