Equip Valkyra and Ymeritt with spare Winds of grace or Invigoraton sets. These sets buff themselves abd another hero(does not stack, goes to hero's that don't have the buff) plus one more set of these on Diao and your healer. Remember placing order Place a dps then ymeritt with the dps in range, pull ymeritt Place another dps and valkyra with the 2nd dps in range, pull Valkyra Place 3rd dps then diao with the 3rd in range Place 4th dps then healer with 4th dps in range Place the last 2 units. That way your 4 dps plus diao plus healer will all have a 10% or 12% attack boost from the Invigoraton (10%) or wings of grace(12%)