Downside of Micro-Nikkors outside of Macro work?

I used to own the tamron 90mm 2.8 macro. It was excellent as a macro but it didn't quite attract me as a portrait lens even tho the manufacturer claims it also as a dual purpose lens. What I found was the shott werent sharp as my dedicated portrait lens 85mm 1.4d. It the opposite of what is claim here of too much sharpness. The lenght 90mm is great for that but also 2.8 leaves something to be desired when dof is concern. I tried to do research on this lens all around the internet but only found one article and nothing else. Looks like it never catched on even tho if you on a shoe string budget its feasible. Better than a kit lens tho.