Bloody coins, which you get through the Timeless Isle's Fire-Watcher's Oath, have recently undergone some major changes. The drop rate was nerfed when the Censer of Eternal Agony was nerfed, and collecting bloody coins became a head-desking activity. Fortunately, that's changed now.
Hinted at over Twitter yesterday and posted on the forums last night, the Oath now guarantees a 100% drop rate on the bloody coins in Battlegrounds. Just get the killing blow and you'll be set. The full blue post as follows: