battleground has never been about killing healer first. all you need is to just focus fire down the enemey with the lowest hp/resilience, then move on to the next. there is not a single healer in the world who can outheal 6 or 7 dps smacking the same guy unless the dpsers are shit and do 1k dps and backpedal or some crap.
the side with the better dps always wins the bg, just look at the scorecard every match.