Forge for MC152 (1.5.2-7.8.1.738) doesn't seem to adhere to the gamedir option, as far as I can tell.  It expects the Forge-related folders (mods/coremods, config, lib, etc) to be in %APPDATA%\.minecraft as with the old launcher. 
  
Is this something that would need to change in Forge for MC152, or am I just not setting up the profile correctly? 
 
    "Mod52_Seek": {
      "name": "Mod52_Seek",
      "gameDir": "C:\\Games\\Minecraft\\Mod52_Seek",
      "lastVersionId": "1.5.2.forge",
      "javaArgs": "-Xincgc -Xmx1G",
      "playerUUID": (censored),
      "useHopperCrashService": false,
      "launcherVisibilityOnGameClose": "keep the launcher open"
    }
 
  
With the Forge'd Minecraft version using the default launch parameters, 
 
"minecraftArguments": "${auth_player_name} ${auth_session} --gameDir ${game_directory} --assetsDir ${game_assets}",