Hand of Chayula applies mark to weird target

So, I have Hand of Chayula supported with Sniper's mark, Profusion and Conduction.
Due to having AoE I noticed that Mark is not being applied to the main target of the attack, but to some other enemy in range.
I think it should try to apply mark to the main target of the attack, which is most often a boss or rare mob.

I think what's actually happening is, that if the Hand of Chauyla crits, it consumes Sniper's Mark right away.

Another forum posts says marks and curses like sniper’s mark and despair are not applied with the initial hit. In other words HoC damage is calculated before applying socketed gems, so criting with HoC does not generate a frenzy charge with sniper’s mark.