On a computer with high ping, (45ms just to connect to my ISP..., Asia Taiwan), often times battle sprite skills wont fire when I press on the corresponding button. I will get the finger pointing animation but no skill is used. When this happens I just keep on pressing on the hotkey and eventually it will go off (obviously this is not a solution, the skill timing is waaaay off).
However when I use a computer with lower ping, (5ms to connect to ISP, still in Taiwan), there is no such issues.
BS key assignment:

1: 8
2: 9 and mouse down
3: 0 and mouse up

PS. I use mouse scroll to trigger BS skills, but had to assign the numbers as first key in order to avoid the super long hotkey indicator text below the skill icon.