Yeah, you'll find yourself drawn back to Dev even if you do find someone else that you like, haha. It's just the way it works. However, maybe here are some that you'd like? Artists and albums.
-The Omega Experiment, as the guy above me mentioned. Singer is a great guy from the forums actually.

-Baroness, though the vocals may not be what you like totally. I recommend you start with Red Album
-Mastodon. I know you already mentioned them but listen to The Hunter if you haven't already.
-The Ocean. I really like Pelagial. There's some growl type singing, but he's got a nice voice too.
-OSI. Office of Strategic Influence or Blood. Singer is the original keyboardist for Dream Theater, Kevin Moore.
-Porcupine Tree. Deadwing, In Absentia, Fear of a Blank Planet. Their early albums are pretty open and experimental, sort of like metal Pink Floyd. If you like that then I recommend The Sky Moves Sideways
-Riverside, Anno Domino High Definition. A bit more mellow, but has it's heavy parts.
-Textures - Dualism. I might get some rolling eyes for this one, I don't know. But I love this album.
Hope if anything you find something new you like.

Edit: Oh jeez, this post is two years old. HAhahaha, well, if you're still around, or if anyone else is curious, here you go. Oh lawd I feel foolish.
