Below is one example of "hero: null "but it is happening on all games in json feed with Deathwing as a character. Bans appear to also be showing null for that selection when Deathwing is banned.

http://hotsapi.net/api/v1/replays/23557610

hero | null
hero_level | 9
team | 1
winner | false
blizz_id | 506598
party | 0
silenced | false
battletag | "xnick#1820"
talents |
1 | "DeathwingMoltenBlood"
4 | "DeathwingDragonsIre"
7 | "DeathwingSkyfall"
10 | "DeathwingBellowingRoar"
13 | "DeathwingRuination"
16 | "DeathwingElementiumPlating"