It’s not their magic anymore the moment it hits Zora magic
Why would it not be?
The guidebook itself words it as Zora just repelling their magic back at them and that their own power is what's beating them. It doesn't turn that magic into Zora's or anything like that.
at least use a similar AoE spell like Another Atlas which passively disrupts the flow of mana within it preventing projectile attacks from being formed except by the caster herself
Atlas
does affect the caster but in a bias way as it comes from Compass Magic. The whole point of Compass Magic is that, like a compass showing a direction,
it directs stuff to another directions so instead of hitting point X they hit point Y.
All Another Atlas does is make her able to use said Compass Magic around the entire area so the entire direction of where magic is going is messed up due to how Kivn is making the compass constantly rotate so since the direction will never point at her, their attacks will never hit her, her own magic is also being affected by her own compass magic but instead of making them rotate endlessly,
compass magic is making it so her attacks will never fail to hit her opponent.
Kivn is also an elf.
Elfs are all beloved by mana which
makes them immune to attacks that take control over the mana of the area just like Zenon's Absolute space, this even being showed
by Yuno. So
even if you think it should still disturb Kivn's mana... it wouldn't.
Dream World which puts anyone within it to sleep again except the caster
Dream World does
what Dorothy herself wants, if she doesn't want anyone to sleep, they won't sleep. Dorothy notes that it is a good place for her to talk to Noelle, and it is never shown Noelle being affected by any drowsiness as that isn't Dorothy's intention at that moment, she even calls it the perfect place for secret chats and says she normally punishes bad people by trapping them there. If Dream World always made everyone in it sleep, then Dorothy would be literally killing people since Reve said if you sleep in it,
you never wake up.
If that doesn't convince you, it is worth noting that
Reve was indeed yawning and getting sleepy herself so it's very likely she was being affected as well but could resist it unlike the Black Bulls and this is entirely possible considering how related her character is to being sleepy and well sleeping.
the Presence of the Demon King, which affects everyone except Dante himself hell in some cases even a spell something like Gravity Singularity.
Except Dante
is being affected by his own gravity. You can see the gravity is affecting him by the lines specifically on his body when he uses it. Dante is just extremely resistant to Gravity due to his raw strength/power. It's quite literally proved later by Yuno and Mereoleona (Post-Growth) that people with enough strength/power can even resist Lucifero's Gravity while Captains couldn't (where we also see gravity lines on Lucifero himself). It's also why Dante's black-hole "doesn't affect him", he's too strong for it to do so significantly.
Same goes with his other spells it affects time itself, yet that never stops him from affecting the time of targets he only wants. We literally saw this after the final fight lol. (Also the link isn't working but I'm pretty sure you are referring to Patri statement)
Because he affects the flow of time
locally, aka within the range of his attacks. It's why Party is able to avoid his time manipulation after what he said about it affecting the flow of time, and why light magic is a natural enemy to time as even though it's messing with the flow of time itself, the "average time magic user" would never hit the "average light magic user" due to how fast they are.
Extra point here, if they could just exclude themselves from their own magic's effects then Nozel would have no reason to be in pain of maintaining his Silver Guardian spell as the poison would not affect him, but it does.
