I see Boril being debuffed as more a defence issue rather than attack. It’s why his counterattack has to be timed correctly. For example, don’t activate Boril’s special when an enemy debuffer is about to be fully charged.
But with those specific characters, Boril’s counterattack could be reduced because of the additional defence provided by Wilbur. Richard may do better, stat dependent, in that team. Your blue attack will depend whether you anticipate relying more on tile damage or special damage.
Positioning for attack teams is arguably less important than positioning for defence teams. With Boril on attack, just make sure he’s in one of the middle three positions because of his special. The enemy AI will randomly attack characters in the lineup, so the tank position (the middle) means less in this scenario.
The other thing is… what purpose does this attack team server? Raid? War? Map? You might be better off colour stacking for better win ratios.