View Single Post
You don't mention what version of OmniPlan you are using. OmniPlan 2 has options in the Task:Assignments Inspector that would be useful to you:

I think you would have to apply this setting to all of your tasks, but you can select the entire document and do it en masse.

I have to say it's a little weird to think that a development task is going to take the same duration no matter how many people you have work on it...