Today's Daily Heroic (Tuesday, March 29th), will not award Legendary Marks when completed. Please refer to the following help article for more information:
https://www.bungie.net/en/Help/Article/14206
[url=https://www.bungie.net/en/Forum/Post/198215175/0/0][b]DPS Bulletin: Daily Heroic will not reward Legendary Marks on Mar. 29, 2016[/b][/url]