I think they work great in TFotG, as I feel like I'm playing a miniature GOW level, only with human opponents, not AI, but I think they take away from FotG. The arena should be about straight up combat, not getting points by collecting red orbs. Any of the Treasure of the Gods you can acquire in FotG can just be shunted over to TFotG.
The more I play FotG, the stronger I feel about this. It makes arena matches feel clunky.