Make the drop ship that comes in play an actual role in the battle. Players can choose to either ignore it like they do now, and take advantage of it by attacking the sucker. Dealing enough damage will cause it to lose control and either crash into Phogoth or slam against a wall as its spiraling out of control, causing a section of the ceiling to collapse and hit the massive Ogre. The result either which way will leave Phogoth stunned temporarily. Include Sword Bearers in this encounter who regularly drop swords that the players can pick up. While Phogoth is stunned, you can actually get close enough to it for up close damage. If you use a sword to attack his weak point, you'll stab it into him, resulting in a HUGE chunk of health being lost and making him take double the damage (more than you did) whenever you hit his core.

Mal you are killing it with these ideas!! This sounds really interesting.

I hate boss battles that are just repetitive. Need to mix them up and add different options for players to approach a challenge, ya know? Keeps things fresh.

Give Phogoth more attacks for an extra element of unpredictability. Maybe he could throw stuff, charge at people, and/or do a roar that disorients you in addition to his laser eye and ground slam.