I am going to keep this short and sweet, so I hope you take advantage of this before it is fixed lol. And, whilethis isn't entirely an exploit and it IS more of a bug, I feel it is worthy of posting here in the exploit section, considering it is not working as intended.
Basically, if you enter a Rated Battleground match, and you look at your Battle Standard, it specifically says on it in bright red letters "You cannot use this item in Rated Battlegrounds" -- or something like that. But, this is not actually true. While it says that, you still can freely use them AND they do actually boost your HP like they should. I hope you guys take advantage of this whilst you can!
TIP: I would try to only drop it in bushes, behind trees/rocks, etc -- just because another team probably could report you for using this and pvprs are pissed people when they lose and are more inclined to report the other team for anything lol, although it would be quite easy to explain to a GM that you didn't know you couldn't use it in rated BGs, you didn't read the new tooltip lol and you just had it hot-keyed like in regular BGs.
Anyway, ENJOY!