Sounds like you were solo tanking this, not really something you would want to do. Never had any issues myself with reactive shield not being available when doing this, just did it yesterday. With 2 tanks, timing always works out perfect, no need for adrenals.
That said, Vanguards do need a buff of some kind. Our tank cool-downs basically suck. If things go wrong, none of our cool-downs are good enough to save us from certain death.