The chances of getting into a deathmatch battleground are currently too low. You can spend a whole evening and many hours doing battlegrounds without getting into a single deathmatch, even though that's what I and I'd argue most serious PVP players want to play. It's mostly casual PVP players who'd prefer one of the objective modes and their interest in this regard should really be secondary as they have enough other things to do in ESO as it is.
There should either be a deathmatch only queue again or the chances of getting into a deathmatch vs. one of the objective modes should be 50%. I assume it's currently 20% and this doesn't make sense considering how similar the objective modes are, particularly domination and crazy king. Deathmatch is not just one mode among many, but totally separate from the objective modes in its essense.

Let people play what they want and if the player base isn't large enough to support two separate queues, ZOS could either try to increase the player base by making battlegrounds more attractive to play via rewards or new content or at least make deatchmatches more likely to be picked among the game modes, so that people who want to play them aren't forced to play somethings else 80% of the time.