There are a number of problems that affect the DoA's to certain degrees (I'm mainly familiar with DoA2 and DoAU though--not as much DoA3, but I think it runs pretty close to form).
* Counters in general come out faster, have a longer active duration, do more damage, and are faster to recover from (and hence for an opponent to respond to a miss) than they should be. Oh yes, and unreversable.
* Throws in general come out a lot faster, and do a lot more damage than they should. And are inescapable.
Both these tend to make the game turn into more of a turtle match the more you know about the game.
As well, too many of the normal moves do disproportionately strong damage and have too-good tracking properties, which counters what's supposed to be one of the stronger features of 3D games versus 2D games--sidestepping. (Some exceptions exist, of course, like Hayate's fast-as-nuts one with
this guy used to
beat the top players in Japan in DoA3, admitting he had only started playing the game a few weeks earlier.)
Even the boards themselves--while busier and more imaginative than other games--add a bit of annoyace, as it punishes one in the corner by adding extra damage and giving the opportunity to tack on more combo strings...
What DoA tends to be is faster, more frentic, and has the tendency to even out player skills with more randomness (though two more experienced characters will seem to go off in their own direction trying to abuse the strong points). It's certainly no "party game" in the way SSBM is; nor is it trying to be, nor--obviously--does Tecmo or Team Ninja WANT it to be. It is trying to be more friendly and accessable to general fighting game players, but the problem is even though that's what they're targetting, and they deliver it in the best-looking package, and they can show off many modes, boards, and deliver a solid online experience, AND they deliver the best boobies in the biz...
The sales just don't bear out that they're tapping the general public they're aiming for. And in the meanwhile, they are missing most of the hardcore community that looks at every new fighting game as another opportunity to suck every bit of marrow from it and give them something new and cool to fixate on.
They need to change their gameplan
somehow.