If Epic Battlegrounds do not have a good reward to encourage sign ups and are not adjusted to last longer, we risk sitting in queue for longer than games last. That sucks from a game play perspective. I personally would be very unhappy to have a game last 12 minutes after being in queue for 20.
Our thought was that the Brawls feature provides some of that gameplay, where a battleground is in the spotlight for a bit. Granted, not all battlegrounds have a brawl but we still plan on adding more as time goes on.
One thing we've added in Battle for Azeroth is "Call to Arms" for War Mode. Each week will be a different zone quest to kill a number of the opposing faction for a conquest reward (both Horde and Alliance are sent to the same zone). You can find it in the hubs in Boralus and Zuldazar.