Well, there's obviously a lot of rotation in the list of deo'iel, as due to how popular they are and the convenient way to escape the law they represent they have a constant high recruitment-rate, but it is also fairly easy to die doing deo'iel work (the veteran deo'iel in the innermost circles tend to be the one with the highest survival-rate)... So the actual number of deo'iel tends to fluctuate a lot, but usually they'll have between one and two thousand agents distributed across their various bases. They can cover a [I]lot[/I] of ground and a lot of monster-occurrences with that, especially with most ordinary requests or situations being assigned just one or two teams (so six or twelve individuals). And even then, a bunch of them have time to train the newbies.
(Most of those one or two thousand deo'iel are obviously of the outermost circles - first through third - and only a hundred or so of those have been recognized as competent enough to get to the fourth circle. There are maybe seventy deo'iel fifth circle across northern Kirirak, and less than ten sixth circle-members. Oh, and just three deo'iel of the innermost seventh circle, the overseers of the Order.)