In my Bibracte saga here on the Atlas Forum, we ran a Dimicatio.
I had someone BSG, and then designed a character to play, hes essentially designed for the Dimicatio, and other things. He's the kind of Tyatlus that wants to outdo some of the best from every House. He was geared to outdo the Flambeau at their own event. Multicasting is just that, multicasting, multiple spells, and as far as I'm concerned actually vioaltes the rules of the Dimicatio, which governs one spell only. Furthermore, mastery abilities such as obfuscated casting, fast casting and quick casting are all very important, in addition to virtues such as quick casting and a high Quickness characteristic. See Marcus' character sheet. I asked Peregrine_Bjornaer to run the event and basically come up with competitors. I don't think he pulled any punches, but I'll leave it to him to comment about that. I didn't expect him to win, but I did expect him to go pretty deep into the competition.
If he competes next tournament, he has some different ideas.
As to the Flambeau tourney, one of the things I found interesting is that the Dimicatio, IIRC, is supposed to be open to those who did well in the Certamen tourney, which in my opinion has completely different play. Characters who are designed to do well at Certamen may not do well at Dimicatio at all, and vice versa.