I just found these DO options and I'm test driving (3x) Cannon and Beam DO buffs with Cannon and Beamer setups.

I'm thinking the beamer setup bonus might actually be a more interesting. Running thru CRF III/CRF II is already pretty nicely paced, but being able to send out another BOIII/BOII quickly could be a very compelling 10-30K crit attack.

Purples are a little pricey (10-15 million), but Blues/Greens are readily available at much better prices. Time buffs are:

Purple = 30 sec reduction
Blue = 25 sec reduction
Green = 20 sec reduction
white = 15 sec reduction

I have gone with blues until I find purple sellers in the 1-5 million range.