missing fleeing mob

[Wudan]

I have a problem with this one particular game mechanic

I solo most of the time (shaman) and when I get the mob low enough so they start fleeing, I suddenly start missing A LOT with my 1hb or piercing (both skills maxed) when I’m trying to finish them.

I mean like 5-10 times in a row... while it never happens when I’m tanking the mob - I hit at least 2 out of 3 times.

What sense does it make to miss so many times in a row when trying to hit slowly fleeing mob in their fucking back?! I usually just lose my patience and cast DD to finish them off which only wastes my precious mana.

I don’t see any logic in this and not sure whether it was like this back in the day…. any thoughts on this?