Season 3 was terrible, season 4 was amazing, and it has been downhill ever since. Dexter has gotten increasingly lazy as the series progressed.
Do you mean the character Dexter Morgan, or the series as a whole?
I don't know what the word I'm searching for to describe season 8 is but... maybe that's it. 'Lazy.' There's something really meandering about this show now, like it's wandering off somewhere. Maybe that's how it ends. Dexter disappears and no one knows where he is!