Generally I would say yes, ...

Generally I would say yes, equalization does make sense.  Like most things, there will always be exceptions to the rule (e.g. items toxic to bacteria should be treated separately from things that are biodegradable).  Equalization often levels out issues that would otherwise make wastewater treatment more difficult.  For example, streams that are low in BOD can be blended with streams that are high in BOD providing a more uniform food source for a treatment system.  Also, temperature extremes, pH extremes, etc. may also be normalized making life for a biological system more viable.