Quite literally then, as he's currently dead in New 52 continuity. Then again, I'm sure there are ways to write him back into action, but "The Big Burn" worked pretty well as a type of "last story" for Harvey Dent. I honestly wouldn't mind if he stayed dead for a while, with some acknowledgment of what it meant to Bruce Wayne to finally have to give up on his old friend.
Otherwise, I don't think there's been a good Batman v.s Hugo Strange story since way back in Gotham Knights. Bring him back into the comics, and focus on his obsession with replacing Batman rather than messing with Bruce Wayne. From the more obscure ones, there are a lot of Grant/Breyfogle villains that have been quiet for way too long. Kadaver, Ratcatcher, Cornelius Stirk, Ventriloquist & Scarface... All names that would work great in smaller, more intimate stories than the stuff Snyder and Capullo are doing in Batman.