[whpalmer4]

There's no appreciable cost to having additional contexts, within reason. I would argue it is better to have "too many" rather than "too few" as "too few" results in seeing tasks displayed which you cannot actually do. If you just have a Sales context and are forced to throw tasks which can only be done with Joe into that context, every time you pull up the Sales context and Joe isn't present, you see all of the tasks which require Joe cluttering up your view. Looking at a hierarchy of contexts, grouped by context, you don't see anything for contexts which have no actions.

If you have difficulty with having a Joe context at several points in the context hierarchy, make a perspective to collate them all together.

Rule of thumb: if OmniFocus is frequently showing you tasks which you cannot do, you've either assigned the tasks to the wrong contexts, your context structure needs refactoring to capture the distinction between the tasks you can and cannot do, or both.