Harvest bosses need their invulnerability phases removed

I play a summoner. My minions do a good job drawing aggro from these bosses. All of them like to charge and move around a lot, putting themselves up against walls and obstacles. Once I reduce their HP to a certain threshold, they become invulnerable until they enter the next phase properly.

And that's where the problem starts.

Because the bosses love moving around with their charges and leap attacks, they constantly put themselves against walls which prevents them from transitioning into the add phase. My minions aren't intelligent enough to understand that the boss is ready to move to the add phase and will keep wailing on it until I run far enough away to force them off.

And to make matters worse: If I can't get the monster to move to someplace more open, they'll continue spamming their abilities that make them run around more, making the process take longer.

If I have the DPS to kill these things outright, I should just be allowed to kill them. There shouldn't be a forced invulnerability phase. Alternatively, you greatly reduce their "required area" range to allow them to change phases. A third option is to make the monster have phasing, passive, and force them to wander into an open area. It's not like you don't have the tech, you literally made the Incarnation of Dread move to the center of the arena before he starts the petal collection phase.

Just, do something to make these fights less annoying for summoners.

They've also been super buggy for years and they can't seem to fix those phases, so +1. Immunity phases are a cheap way of designing a boss, the harvest bosses should get the Catarina treatment except remove all the phases instead of leaving the boss with 1.