User blog comment:Zaiku K/The Next Dolls: Only Optimized for One Major Battle?/@comment-10534118-20140906032547

You can call sheer coincidence on which Next Doll guarded which seal for the specific Heavenly Knight to go to. Unless said Next Dolls traced their rivals to their respective towers and intercepted them.

However you stated that an easy switcheroo would have removed all issues of the Next Dolls. This is an excellent point to question why the Heavenly Knights never did this. However we have to look at every instance that the Heavenly Knights fought their respective Next Dolls.

In Granberia and Alma Elma's case, they were both exhausted from their fights with Luka. So a simple swap wouldn't have guaranteed a win. Erubetie was forced to 1v1 Amphisbaena in Undine's Spring. Tamamo and Tsukuyomi had no previous fights before their fight at the Ivory Tower.

As Alex stated, if a certain Heavenly Knight fought a Next Doll that was beyond their programmed counter-measures. It could have resulted in a Next Doll retreating. In each of the Next Doll's rape scenes, it depicts them leaving the Ivory Tower to go attack Luka, not caring that said tower was unguarded. Meaning Luka would have had to deal with both Rapunzel and other Next Dolls while the seal on the Angels was applied.

As for Rapunzel; She's unspecialized due to her design to breed new Next Dolls. She specialized in pleasure attacks and has an insatiable desire to mate. The only counter she'd have is Luka himself, but the spirits got unsealed sealing her fate.