I can only speak for myself but yes, I love the random brawls. They are great for questing and they are fun.

With the random brawls, where you get a predefined deck, I usually rack up somewhere between 20 to 40 wins (and I usually only do my daily quests). With the brawls where you have to build a deck, I usually only play until I get my free pack.

For me, the random brawls are quick, replayable, exciting fun. I wouldn't need the deckbuilding ones at all