I hesitate to provide a contrary view, but I can vouch for a 2 micron primary filter working just fine and being beneficial if you address underlying problems. My layout is a Racor 2 micron primary, and the standard Universal diesel secondary on the engine. I have 600 hours on this arrangement through all sorts of conditions.
When I switched my fuel to a % of biodiesel when I bought our boat, I knew there would be sludge in the 20 year old infrequently used tank wanting to come out. I immediately switched the Racor to 2 microns so as not to suck any crud into the injection pump. I changed filters a few times in the first 100 hours and they had a moderate amount of crud each time. I then did a manual self-polishing by routing the electric fuel pump back to the tank and running it a while. By the way, on my Universal 5432 the fuel pump is external and electric.
Anyway, I've now put 600 hours on this arrangement and change my primary and secondary filters every year out of an overabundance of caution. I have motored through truly nasty conditions and still my 2 micron Racor is essentially pristine when I change them every year.
I trust in the wisdom that clean fuel makes a diesel happy, and since my fuel pump is electric and external, and I always carry a spare just in case (though I have yet to need it in 5 years!) I have no concerns about the added strain on the pump.
My view, simplified and boiled down, is that if your fuel tank is dirty enough to clog a 2 micron filter in any serious way, you have bigger and more pressing problems than your fuel pump. Clean the tank, install a 2 micron, and you will never again have to worry about any damaging particles hitting your delicate and expensive fuel injection system.
Here's a picture of my secondary filter (downstream of the also clean Racor R15S) after 150 hours of use:Stories of Aeolus- Our Gulf 32 Pilothouse: Secondary fuel filter change and she's spotless!