I think most of us are on board when I say BL3 may have overused Immunity thought the game. There are some bosses like Troy or Tyreen where I would expect them to have the odd dodge the attack phase, or hit the things to damage the boss mechanic. I think giving some enemies like Anointed militants immunity attacks was a flat mistake.
Back to Boss designe some bosses like Aurelia miss use the immunity in the sence that she uses it far to often for how frail of a boss she is. In addition the animation is slow causing a break in the fight pace. Wotan also gets immunity but for a far more sensible reason. He is transitioning phases and they want player to see that something is changing and they need to prepare. In Aurelias case this is unnecessary you just keep shooting her and your good. Now I understand a raid boss or a substantial fight having a couple phase breaks but doing it 3 or more times on menial bosses is tiresome and down right annoying.
My next example is The Rampager. A climactic boss but wow he has long immunity phases with no way to short cut them. Just dodge this thing for x amount of time then get back to the fight. It’s annoying to farm.
In other cases we have good use of immunity. Troy and Tyreen both have Immunity periods based on a mechanic which when preformed interrupts an attack or make them vulnerable. This is the ideal way to handle them. Have a way to stop the Immunity as both are fairly quick and to the point. On the other hand both these bosses have several other attacks that make them immune and ask you to jump though hoops for a minute while the boss drags there feet around.
I understand using immunity to show the player that something it happening but it breaks up the pace of what can be an otherwise energetic fight (wink wink nudge nudge mouthpiece)
Over all it makes some of the encounters feel disjointed. This is part of the reason most people farm Graveward over others. No Immunity. Now I’m not saying make every fight like Graveward because he has the opposite problem. What I hope to see is more clever use of Immunity which is based around mechanics rather then “we show you something now” in the middle of the boss fight.