Does Water Pulse (40% confusion via Serene Grace) ever have a place on a Togekiss?
Confusion, has the an effect on damaging the opponent's HP, 50% each time depending on how long the confusion is in play. However, the downfall being it's only 50% and it relies on a bit of luck. This is even taking into account you get the opponent's Pokemon confused, and, they might switch anyway.
Now, it doesn't get stab on this Water-type move. So, you'll be dealing a 60% BP move any time you are trying to confuse the opposing Pokemon.
Air Slash is a must. Obviously has an advantage over its other attacks. Meaning, it will have a reserved seat when the Togekiss is being made. Roost, Nasty Plot, Aura Sphere, Wish, Thunderbolt, Thunder Wave and Baton Pass, etc. You have alot to compete with, and Water Pluse just can't fit on the set.
The big reason why I don't agree with an open spot for Water Pulse: Togekiss has a wide range of options in terms of working with the team. Common one that springs to most people's minds is using the trait Serene Grace to "hax" the opponent. Air Slash's ability to flinch the opponent is a free turn in its own. That is what Water Pulse is for, right? With Air Slash being the better choice over Water Pulse, you see that you're doing the same desired job with more damage anyway (not taking into account the typing of both moves). Additionally, Aura Sphere will damage things like Tyranitar with a significant difference in terms of damage dealt.
This is why I don't agree with Water Pulse. It hasn't really got a use on its own that it can't already do better with something else at its disposal.