Deathcore can be kinda hard to pin down when you talk bands like JfaC who really drift more toward regular ol' death metal or Ingested who drift toward slam. Then you get the standard-bearers like Whitechapel, Carnifex, and Oceano.
I think, just like most genres, there are great bands and a LOOOOOT of shitty ones. And honestly, isn't it a good thing that there are death metal influenced artists out there introducing teenagers to the heavier music? People bitch that it's trendy and Hot Topic shit, but... ain't that all right? Some 14 year old kid finds a Black Dahlia shirt he likes, listens to the band, maybe a year or so later he's burning through old Morbid Angel and Cryptopsy albums, then next thing you know he's on UM taking suggestions out of the Albums thread.
I used to be a counselor and I knew a bunch of kids who liked bands like Bring Me the Horizon or whatever and asked me for suggestions for when they could go home, and so I'd give them a list of more "trve" bands and then they'd come back to me asking for more.