I've waffled around a bit on that one. For me it's come down to Mori or Ares. Both give about the same level of red on the board, but the tradeoff is skyfall buff or two turns of haste for the rest of the party. A Krishna friend of mine is rolling with an Anaphon inherit which is also welcome as a board clear with red/hearts + haste, but subpar for burst without a followup. Between both of 'em my subs are able to fire off actives a'plenty.