Irrelevant considering they are the recipients of a salary, not a wage, hence breaking down productivity - how you even quantify that is beyond me - per hour is a pointless exercise. I have a good friend who works in auditing who works more hours than that and gets a fraction of what bankers earn, but the point is that he's on a salary, not a wage.
Not irrelevant at all.
You *should* occasionally break it down per hour. If you find that you are working 100 hours a week but pulling the hourly wage of a mcdonalds worker...you are probably doing some thing wrong.
A salary is convenient for budgeting on both sides--you know how much you are going to make and your company knows how much it is going to pay in the next month whether business is booming and you are pulling 100 hour weeks or business is slow and you go home after 40.
That doesn't mean you shouldn't look at the $/hr situation. It would be idiotic not to use hourly wage as a decision making factor. If you could take a 10% pay cut but work half the hours (hence increasing the hourly pay), there are quite a lot of people who would do it without question. Those extra hours might even give you time to start a side business and diversify your income stream while more than replacing the lost 10%.