Well, if you're counting Scourge and Ringil (Ringil isn't very strong anyway though), you should count Tupsimati too, which is MP+6, HP/DEF/MND+300%, MAG+800%, MYS/SPI/DRK+99. That's way better than Scourge's ATK+800%, DEF+400%, PHY+100.
I also wasn't trying to suggest a switching attacker playstyle, but switching a character in with Instant Attack, and then switching Nitori/Nazrin back in, to set their ATB to 7500. This would be unnecessary for Nazrin if her ATB is 2000+ per tick, as Nazrin Pendulum has 5500 delay, but Nitori's Kappa's Illusionary Waterfall has 4000 delay, so this would still speed her up. Though with 2000+ ATB ticks, staying in for the sake of Overheating stacking would probably be preferable. And of course, Nazrin would need to be Awakened...but that was the premise of what I was saying in the first place, that Nazrin becomes a strong attacker post-Awakening. So it seems kind of silly to bring it up as a detrimental point.
The numbered items don't really have to do with Nazrin's damage output either, aside from bringing up that it is RNG reliant, which I acknowledge is its primary flaw. I, personally, prefer to assume that RNG will always be unfavorable, so I would not value Nazrin's potential. But that doesn't change that, on average, Nazrin's damage output is excellent, and she has 4 different elements that she can competently use to strike weaknesses (PHY/WND/CLD/SPI [Start of Heavenly Demise]). How to look at RNG is up to the player, I believe, but Nazrin can certainly be expected to be a primary attacking character, despite the whole item farming angle of her character.
Though regardless, I would like to address the numbered items anyway.
1) While Nitori can act as a solo character, Nazrin relying on Byakuren is not necessarily a negative characteristic, since you would want to optimize your damage output, and Byakuren helps Nazrin do that. Nitori would need a character to buff her regardless, and she would continually need buff maintenance, while Byakuren can do anything on the frontline and Nazrin will be at 100% buffs at all times simply because Byakuren is present. In fact, I would go so far as to say that Nitori's solo ability allows her to contribute to Nazrin, since Nitori holds the +30% CLD boosting skill, which makes Nitori the strongest damage boosting character available to put on the frontline with Nazrin. One could have Byakuren buffing Nitori, and the two of them attacking with their CLD spells. This can be further increased with Akyuu's 50% Boost spell card from her Awakening and potentially the 16% weakness boosting skill.
2) While Nitori's Kappa's Illusionary Waterfall is a multi-target spell card, so far the majority of bosses in Plus Disk's endgame are single targets, and Nazrin is still superior for single-targets granted ordinary RNG. Though this also makes Nitori superior for random encounters, Nazrin has her item farming skills (then again, Nitori does too, post-Awakening) and Extra Steps to take turns after defeating an enemy. The DEF debuff on it also doesn't add much damage, though it does add some, that is true.
3) Nitori is a lot bulkier, but due to how Maintenance works, she's losing out on more damage by taking up affinity/status boosting equipment, so that's not a 100% pro. Still, this is the biggest advantage Nitori has as a bulky attacker, even if it doesn't have to do with how much damage Nazrin can do. For what it's worth, Nazrin has 14% HP regen that Nitori does not have, and 150 VOI resistance that Nitori can never increase with any kind of equipment.
4) and 5) were covered already so I'll skip those.
Regarding the comparison with Awakening Suika, keep in mind that Nazrin's Rare Metal Detector has 6800 delay, so she attacks more rapidly than Suika does with Instant Attack switching, and Suika needs 100% HP to get the 20% damage boost, so she requires more maintenance from multi-target attacks. Though honestly, with how much Iku can demolish the game, that Nazrin can be favorably compared with her speaks enough for her damage output. Suika's damage bonuses are more practical to utilize in practice than on paper, so I'm not going to try to calculate how much stronger (if she is stronger) at WND damage she is compared to Nazrin, but Nazrin is still a very strong WND attacker regardless, whether she's #1 or #2.
As for the comparison with Iku and Suika's bulk, I haven't checked Suika, but Nazrin is fine compared to Iku. As you can see in the stat pictures, Iku and Nazrin have nearly the same amount of HP under equal circumstances (Iku has 5% more HP), but their DEF is almost identical. Iku has much higher MND (about 22.5% more), and she can gain 40% more DEF/MND with her Tenshi synergy skill, but DEF/MND is nearly worthless in Plus Disk. Like I calculated for the Serpent of Chaos' damage, the difference between its Direct Attack and Rasetsu Fist on max HP Tenshi was about 5% more damage, and that was over 100K DEF. Besides that, Nazrin has 100% DEF/MND buffs at all times with Byakuren's presence on the field, 14% HP regen, 150 VOI resistance, and Eyes that Perceive Reality to ignore enemy ATK/MAG buffs (something most Corridor bosses use, though idk if the special ones like Abyss Reimu and Abyss Rinnosuke are ignored by it or not). Her affinities are also superior. She's looking at two affinities at 76 for weaknesses, while Iku has 3 affinities at 75 and one at 90. The 150 VOI resistance is especially important here, as VOI attacks are always the most dangerous in the game, and Nazrin takes 33% less damage from them.
Also, I forgot about this, but Maintenance doesn't work with the Divine Falchion, which is kind of important. It's still stronger than the Tokugawa Statue, but Nitori loses more stats by using it than Nazrin does. She's still overall bulkier and everything, this just affects the degree of bulk and how much more damage Nazrin can do in comparison.
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I somewhat feel that the meaning in bringing up Nazrin's damage output was a bit lost in the direction this topic went in, as it was about Shou's inferiority as an attacker. Maybe, instead of bringing up that Nazrin is pretty much competitive (with RNG) with top tier characters, I should have simply pointed out that Nazrin far surpasses Shou in terms of PHY damage. Regardless though, my underlying point was that Shou's farming related skills can't be used to justify her having lowish damage output, as Nazrin is very much competitive with high level damage dealers, and totally outclasses Shou at PHY damage. Even pre-Awakening Nazrin has superior PHY damage output to Shou with her Rinnosuke synergy skill.