The idea of this game has been reminding me of something (other than 24) but I couldn't figure out what until today.
A couple of books by Simon R Green - the 'Hawk and Fisher' series. They are police captains in a huge city (DnD type) Although it isn't DnD, the city has everything you would expect to find, vampire smugglers, werewolf assassins, crime lords, undead, even gods (the Street of the Gods is full of temples - many of which have 'real' gods! One of the stories even has a serial killer who kills gods!)
There is a 'magical clean-up squad', experimental magic weapons (usually unlicensed.) Instead of a Chloe there are magical 'alerts' which ring in your head e.g. "A large crowd of undead have just burst from the sewers in the dock area - deal with it will you?"
He has other books as well, my favourites being "Blue Moon Rising" and Return to the Blue Moon."