I wouldn't sleep on how much Denrimi did for Ousen Army.
Sou'ou was called out in Hango Arc for being pure offensive general without much defensive capabilities, while Denrimi was someone who could do both. In Atsuyo he was Ousen's first choice for commander of the siege. His army was said to be the most lethal force within Ousen Army, basically doing the job of a finisher and he also had the most to say in strategical meetings, being Ousen's top planer.