One thing to question is what wormers and other meds (including pour ons and other fly deterrents) are you giving your livestock. Sadly many of them will deactivate many of the dung-loving flora

I guess the short answer is that harrowing is never bad (well, when you have a decent sward, anyways, and maybe not if you have lots of flowering weeds in it with seed heads on them), so if you have harrows and time, why not.
As to the dung beetles not getting a chance, I think that all the dung-loving flora will still find the smaller lumps if you spread it out, won't they? Just won't be able to lay so many eggs in one place, those that lay in it where it is. (Don't dung beetles gather it up themselves? But some of the other dung-loving flora lay eggs in it where it falls?)