I've gotten bad experience with fixed master tournaments, since they encourage jack of all trades masters.
Even worse, considering you can choose your minions freely every battle, and have perfect knowledge of the opponents masters, you encourage horrible matchups.
(For example, when playing against Leveticus, a Viktoria player could decide to take 3 Void Wretches, which for the Viktorias is usually a very poor choice that no-one would seriously contemplate, but specific in a matchup against Leveticus that becomes an excellent way to break Levi when he's down. ANd since minion choice is free, there is nothing the Vikks have to lose by that choice)