Was thinking about what the dev's noted and it sounds like having the Bulwark function as a healer in any capacity was never intended (which is ridiculous considering no other class has a heal and no class other than vanguard can recover health). It sounds like they wanted the class to be a tank...but theres no aggression mechanic in the game. Bulwark is easily my favorite class and I think to create a sense of tankiness, heres what I would do:

Upon use of the Banner-

1. Make the banner taunt all area (so larger than the armor restore radius) enemies to go into a MELEE rage against the Bulwark
2. Give all team members instant full armor (4 armor slots) 
3. Make the bulwarks block unbreakable, for the full duration of the banner, from all attacks

To me, this needs to be coupled with a rework of one of the bulwarks perks, so that upon shield bash an enemy is taunted for 10 seconds to the bulwark (see same exact talent in Darktide for Ogryn). 

I think this will give the bulwark that tank feeling without making him weak or easily picked off and will all him to act as a sort of regular interaction starter that allows the team to pick off some baddies while they focus on him.