Anytime you try to pass sooty, yucky diesel exhaust through cooling fins, you are going to have troubles with clogging. Just no way around that.
However, there is light at the end of the tunnel. When ULSD comes out, there are projections and inklings that EGR clogging problems will be greatly reduced. I hope so.
EGRs have always been problematic, even on gassers. They got the gasser issue figured out. Hopefully, they can do the same with oil burners.