If I have 2 does it apply 5% burn? How long does it last, and how fast is each tick?
The ticks, from experience, seem to be one per second and I think last until end of fight.
Also, seeing how every other item seems to stack (if you have 2, the effect is done twice, like having 2 spears of shoujin on a character makes it pretty much ult over and over) I would say it straight up does it twice.
So it does a 2.5% burn, then another 2.5% burn. So if there's no weird math, that gives a 5% burn.