Before the October 1 rework to the tactics line, taking both these traits would cause Shrug It Off to always heal when triggered. Maybe Shrug It Off is no longer being classified as a shout skill under the hood?
What is happening is that "Shrug It Off"'s own requirements are overriding "Vigorous Shout". SIO will only heal if it removes a damaging condition. Tested using burning and weakness. Removing burning heals but removing weakness does not. It also causes it to use SIO's own lower healing value(582) rather than the healing value from VS(1373).