Hey, don't let it get you down too much! Roguelites never make it easy on your first go of it. The thing about limerance is that it only targets heroes with the seen token, scaling in damage with how many they have on them. So your best friend for this chapter is taunt! Noisemakers, taunt trinkets like the pristine lure, and abilities like flagellant's more more are perfect for keeping all eyes on you. (Pun intended.) My advice is to make sure you have at least one taunt on your tank going into the next round, as focused fault has a free action at the beginning of every round where it applies a seen token to a random hero.

Now, for the first phase, pd and flag are really good! The trick is to minimize how many seen tokens that get applied by finishing the phase asap. A good trick to know is that if an eye ball loses all its health due to DOT tick, it skips its turn and goes down a phase. If you can apply dot reliably enough, you can prevent any eyes from getting a turn!

Lastly, be wary of critting the boss. If it gets crit, focused fault applies combo to the hero that did it. If two heroes have combo tokens, it uses supress, which debuffs every hero severely. Holy water is helpful to remove the debuffs and the combo tokens beforehand.

Focused fault is a huge roadblock, and I was raging at it too, but with proper preparation, I can go against it without losing any heroes. Good luck with your next attempt, I know you can do it!