DMC4 suffered from many of the same problems as other early HD titles, mostly. DMC4 was the DMC team's first HD titles and one of the first HD titles from Capcom, and the second or third title using MT Framework. They underestimated how complex and time-consuming HD development was compared to earlier gens. The Cell prosessor was probably another hindrance as well. Furthermore, the 360 port wasn't planned initially. Although developing for 360 was easier than PS3, including the 360 port increased their workload by 1.5 according to Kobayashi.
Not only that, but the DMC team were getting tired of working on DMC, having worked on DMC2, DMC3, DMC3SE, then 4 in rapid succesion. Some of them felt they had spent all their ideas on DMC3. This is from interviews with Itsuno and other DMC4 team members in the 3142 art book.
DMC4 had a lot going against it.
They don't. But it makes for good PR, which is something they really need with SF5 now.