The DoF markings on lenses can lead you astray. Basically, of course, only one distance is perfectly focussed at any time. Distances near that are nearly in focus, and it gets less focussed at closer and further distances. How unfocussed is "too unfocussed" to be acceptable? The DoF marks on lenses are based on a degree of "good enough" that can be very disappointing, depending on the subject.

I generally try to use the DoF marks on the lens for an aperture 2 stops wider than I'm actually using. This leads to "less" DoF, but at a quality of focus that justifies the use of a 120 size camera. If the subject does not "fit" the DoF limits, then I need to do more thinking about what to sacrifice in focus and still get the shot (or consider a tripod and a lower shutter speed).

If you need heaps of DoF, then consider 35mm. They are quite good, you know!