Similar experience with Classic shaving wool fat soap
I've had a similar experience with this soap - the lather I get out of it tends to be rather thin and I have to mix it with something otherwise the lather tends to "collapse" after a short while on my face. This of course could be due to technique and water/soap ratios, but I've tried it out with different brushes and have always had a similar result.
I ended up grating a small amount of the soap and blended that with some proraso and that works better. This, however, seems to defeat the purpose of the product... so to sum up, I get better results with other, less expensive products...