I ain't exagerating.
Ottar's beastification is never said to be precisely a match for Bete's.
Quote: 己の『獣化』に勝るとも劣らない出力を認める狼人(ウェアウルフ)は、左頰の刺青(いれずみ)を歪めた。
The line in question mentions Bete recognizing the power of Ottar's beastification, but the important part is in bold. Because that is the term used for the comparison, and it can translate as "to rival or surpass". That means Vana Arganture may be just on par with Ulfheoinn, but there is also a possibility of it being superior.
The following lines also compare it to Haruhime's level boost:
『鏡』が映す『獣』は先程までの武人と明らかに一線を画している。
まるでそれは、奇しくも、春姫(ハルヒメ)の階位昇華(レベル・ブースト)がもたらす光景とも酷似している。
The 'beast' reflected by the 'mirror' is clearly different from the previous warrior.
Oddly enough, it was very similar to the scene brought about by Haruhime's level boost.
Regarding Ais:
1. I am talking about the black wind, which she didn't use against Asterius. She used both Ariel and Avenger, true, but she never combined them. No one saw Ariel turn black in that fight.
2. Revis was overwhelmingly inferior to Ais with her black wind. Even after she donned her flesh armor which was stated to massively increase her physical prowess she was on the losing end, only keeping up because she received a new one each time Ais destroyed it.
Ais was so much faster that she could go behind Revis to attack her and she didn't even manage to react herself, needing her arm cloaked in the flesh armor to block it for her. And even then Ais raised her speed to a point she could outright overcome said defense.
And remember Knossos' adamantite? That which even a Level 6 Gareth, who between his abilities and high Strength stat definitely boasted Level 7 strength, had to destroy his fists to make a hole in just one of them? Not only Ais' strength grew to the point each of her strikes could make a big hole in Knossos' walls and floors, but even just the shockwaves of her clashes with Revis were cracking them.
Not to mention that we get explicit mentions of Ais raising the wind's power output many times over, so it went way past its power at the start of the fight. Point at which it was already enough to utterly overpower Revis.
Oomori wanted to make the black wind OP, and he certainly did.
About Leon, we already have evidence of him being on par with if not being superior to Ottar. Both the statement of him being the only one able to hold him back, and Ottar's own comment indicating Hildis Vini's shockwave is inferior to Leon. The evidence clearly points towards that. If that creates inconsistencies, well, you know how Oomori is.
In Astrea Record we got a statement of Finn boasting power above his actual evel due to Hell Finegas. As for Ais, he only trusted her with delivering the final attack, and we had already seen in the very same volume that Lil Rafaga is a match for a full strength attack of Ottar, a Level 7 with his Strength stat maxed out (not mention his Crush DA). He also at least thought it would give him a chance against Revis in SO7. With her being Level 7, only way for him to stand a chance would be to gain Level 7 power as well.
There is not only a lack of evidence against Hell Finegas boosting Finn's status one level, but we also got evidence that supports it. Also, Oomori is right now practically handing out level boosting abilities like candy. You also have the whole Knights of Fianna events making it an even more special ability than it already was.
If an ability being too OP was what it took for Oomori to not introduce it then things like Alfia's ridiculous power level wouldn't happen. Bell's other boosting ability was outright said to be able to boost his abilities past his actual level, and I can't see Oomori making it weaker than that one. As for ways to not make everything easy: it is as simple as not putting Freya and Horn near Bell when he is fighting.
I didn't read all comments, and neither I am arguing about it. I just saw the post and wanted to vent out about this.
Also, I won't bother to read all comments because, well, no, I am not interested, but not everyone that is fine with such an ending likes the idea. I have a group of friends where it is talked about it normally and treated as a fact not because it is liked, but because it is clear we ain't getting anything better and have come to terms with it. But like I said, I haven't read any comment, so I don't know if that applies to anyone here.