yes once they put in the game a HQ Tab then a CEO or Operations officer can see a total of Defence strength for the combine in HQ  right now you can't because there is no HQ tab I did however suggest that idea to the game support about a HQ Tab that was going back a while ago

Anyone know if there is an easy way to determine total strength of defense in a HQ?

Commander..Plarium is working on a feature that will enable the CEO to see HQ strength...Please be patient as these things are not done quickly..but hopefully we will see this feature added in the not to distant future,,It is a very good feature