Genuine question for fellow vanguard mains, is it ok to abandon the frontline to protect the supports?

Clip above is an example of what I mean

And whose job is it exactly to protect the supports? The dps or tanks? Cuz sometimes when I fall back to help the backline our dps get decimated and the enemy pushes through and other times when I hold the frontline our supports die and we lack the heals necessary to continue the fight and lose space