i'm in the same boat.
i think its just a fault of what's available in global right now. iirc KR/JP have ways to spend stamina outside of story mode and it gets used up quickly.
the only way to get rid of it now is to leave your phone running story mode 24/7 and i'm not too keen for it honestly >n<
thx for the insight about poison/bleed, it's helped me alot.
tho i want to point out that g.chang'e's triple hit is on her slide skill so she only works if there's someone with burst to followup. more often than not syrinx refreshes the fortitude before g.chang'e is ready again.
i've been wondering about the difference too, charge *speed* vs charge *amount*.
notice how when you do an auto attack or get attacked the charge gauge jumps ahead a bit? i think charge amount affects this.
whereas charge speed is just making the gauge fill quicker over time.
but thats just what i found from playing around with both, sorry i dont have any hard numbers for you
as far as the leader skills go, they probably have nearly equal impact. regardless i would go with chang'e because her cd reduction slide is very powerful