I find bombs are fairly useful even when the boss doesn't take damage from them. For example, against Flandre's Cranberry Trap I've yet to figure out how to not fail on it, so I sometimes have to bomb it to avoid dying. Flandre won't take damage, but it at least gives me some breathing room and buys me some time to set up for another assault.
As for rage... Well, stage 4 and Satori are giving me a lot of problems as Patchouli/Marisa. What's worse is I know the trick to all of the cards, I just keep screwing up... I really can't stand Princess Undine, but at least Philosopher's Stone isn't as hard as it is in ESoD (and looks a lot more awesome, to boot).
Nitori/Marisa on the same stage is also a pain... With absolutely no spread to her name I have to use more bombs than I like (I still can't reliably deathbomb... Maybe half the time I can do it), especially on the part after midboss Orin, and.... Is it just me, or are Satori's version of Nitori's cards harder than the actual Nitori set? Because I can fight Nitori in MoF almost perfectly, yet Satori's version of her attacks always get me...