If the hairloss is that agressive then using only dutasteride is not enough. You need a topical that can stop all androgens on the scalp not only DHT. You also need some growth stimulant like minoxidil. And even then it all depends on how you respond to these meds.
Honestly I think it might be worth trying. I am going to try RU58841 for 6 months and see what happens. To your original question, my diffuse thinning was incredibly sudden and aggressive but right now my hair still looks pretty good when styled and probably better than it did 6 months ago. In hindsight my hair has been thinning ever since I turned 19. The first 2 years were very very slow thinning that I barely noticed. Then it got aggressive at the start of 2018.
My dad was already the full nw6 at my age (22) and from what I hear he was also an aggressive diffuse thinner (diffuse+receding). Nobody can tell I am balding yet and I do think I am slowing it down. I am gonna try everything that is out there right now to find a regime that can maintain without harming my dick too much. I just don't think attacking this problem with only one medication is enough if you plan on keeping hair long term.
I think I may have some body dysmorphia as well, my hair has pretty much stayed the same throughout the past year. Yet, I always have some inclination to tell myself that my hair looks much worse. I don’t know if it’s really that aggressive in the first place. By all accounts I am lucky to still have a “decent” head of hair at 21; could have lost it all much younger, but thank god that wasn’t the case.