i only played DMC3 & DMC4
but i'd have to agree w/ the TS that DMD in DMC4 isn't really as tough as the other DMCs especially DMC3 (sure about this)
when i was playing DMC3, i could barely finish it and my rank really reeks, either C or B, plus it took me around 1 week just to finish it
but in DMC4, its not really that hard for me, unless if i'm up against chimera assaults, i just installed DMC4 in my PC this friday night and i've already finished Human, Devil Hunter & SoS all w/ S ranking and i'm at Mission 15 in DMD w/ all its previous missions S ranked.
But still surely CAPCOM has already predicted this response to the ease of DMD so maybe that's why they added two more difficulties, HaH & Legendary Dark Knight
BTW, just for those who haven't read this article in wikipedia
one of the characteristics of DMC1 that really WOWed the critics was it being considerably challenging, however DMC2 was given a lower ranking than DMC1 because it's challenging essence wasn't there anymore, but w/ the release of DMC3 the challenging gameplay made a comeback though it seems that CAPCOM put to much effort in it making it too challenging,
the easy difficulty of the english version of dmc3 was already the hard difficulty in the japanese version.
guess this article explains alot. BTW sorry if my grammar is sometimes twisted, english not being my national language in all.