Yeah, Reisen definitely needs more respect. She absolutely destroyed 16F boss for
Team Unappreciated. The great thing about Discarder is that it lowers offensive as well as defensive and speed stats, unlike Komachi's spell. A boss's nukes aren't so threatening if they're kept at -40% MAG, you know.
And contrary to what some believe, debuffs still remain reasonably viable for many battles even after 16F. Some are under this notion that debuffs are worthless after 18F (who is infamously immune to all status and debuff effects), when in fact there are plenty of bosses that are vulnerable to them, some dreadfully so.
Cosmic - Lacks all resistance to debuffs.
Aria-singing Torustory - Very easy to destroy is MAG stat and render its attacks pathetically weak, just one of the reasons why it's considered the weakest of the final boss's summons.
Beast of Centuarea - Remarkably low debuff resistance, especially for a Bloodstained Seal boss.
Bloody Papa - Even lower debuff resistance than the Beast of Centaurea. Don't expect the MND debuff to help your magic hurt him, though, but the DEF, SPD, and especially MAG debuffs could mean life or death here.
Agastobruama - For a Plus Disk boss, he's got pathetic resistance to debuffs. It seems almost every boss that gets Strengthen Jutsu is also cripplingly weak to debuffs.
Kedamagrammaton - Its debuff resistance drops to 0 while its charging up for its multi-turn Rankain attack. Spiking its MAG with Renko just before it goes off will severely weaken Rankain's power, not to mention bringing its massive 320,000 DEF/MND down to more reasonable levels.
In fact, the only bosses that are immune to debuffs after 18F are Rainbow Phoenix (who even remembers this one?), Shikieiki, Utsuho, and that floor 1 Bloodstained Seal boss with the really long name. Every other boss ranges from average boss debuff resistance (Yuka, most Plus Disk sigil guardians) to high but still doable (Hibachi, Serpent of Chaos, even the **WINNER**).