Dusty has said the reason he splits up the lefties in the lineup is because he doesn't want both Votto and Bruce to have to face a LOOGY in the late innings. The problem with his reasoning is that putting only one batter in between Votto and Bruce has not prevented the other team from putting in a LOOGY to face Votto and leaving him in to face Ludwick and Bruce. What this means is that splitting up the lefties has never actually accomplished what Dusty wants it to do.
Furthermore, using Ludwick as the gap between Votto and Bruce doesn't punish the other team for putting in a LOOGY to face our #3-5 hitters because Ludwick does not hit lefties well and hits RHP much better even though he is a right-handed batter (Ludwick career .240/.322/.452 vs LHP and .273/.339/.471 vs RHP). It would be smarter to put Phillips in the middle because he hits lefties much better than righties (.293/.341/.491 vs LHP and .265/.314/.412 vs RHP) so putting him between Votto and Bruce would help get him more ABs vs LHP and provides a stronger deterrent to the opponent for leaving the LOOGY in to face three Reds' batters. If you really must split up Votto and Bruce (even though it doesn't work) then Phillips is the guy that should be in the middle.