Suretrak PM program.

Although I think that the "culture" of overtime in architecture is ridiculous - it seems like in this situation there could be an understanding with your salaried employees that overtime one week (or month) could translate into leaving early (once the nessessary work is done) in the famine times when there is nothing to do. In my opinion the worst part of your scheduling dilemma is having minimal work because the employee has to fake being busy - which is a real moral buster.

Sometimes in an office with a lot of small projects this situation results from people becoming territorial/possessive about "their" little projects. If you look around and see any employees who regularly act somewhat "control freakish" at the same time that they are perpetually swamped, then what you may have are one or more people who are unwilling to delegate. It's also possible that you have one or more people to whom nobody wants to delegate - for any number of reasons.
If you are in a low to mid-level position in the firm it may be difficult to do much about the overall situation, other than to make it clear that you personally would rather take on whatever tasks are available from those who appear to be swamped, and at the same time you should be willing to relinquish control of tasks/projcects to others when you yourself are over-deadlined.
If you are in more of a management role then you need to make it clear that:
1. Obviously nobody should be doing nothing - or stretching out minimal work to appear busy - unless they have made the rounds and found absolutely nothing else to do.
If you have people who continuously seem to turn up with nothing to do then it may be a good idea not only to find out these people's personal take on why this is, but also to see whether there is some pervasive reason that others are not giving them things to do. If you've got people who others see as difficult to work with, or inaccurate, sloppy or slow, this may have a big impact on the overall distribution of work.
2. At the same time that the firm frowns on idleness, it should make clear that it does not value or reward the practice of over-burdened people working all night on "their" projects - unless there is absolutely nobody around to whom to delegate some of the workload.

Depending on the size of the firm and the general communication style, a big wall calendar or some calendar/schedule software can be very helpful with this. If everybody is expected to write down - for everyone to see - what it is that he's working on that day or week, it becomes harder to hide lack of work or to hoarde projects.