Flyswatter is technically one of the witch's better attacks, but there are two things it really boasts besides the attack.
1. The ability to Curse.
2. The ability to spawn monsters.
Ability 1 is worthless without having the skill at max level. If you do not max it all the way, you are wasting the potential that this skill offers. IF you really want this skill for a combo ender, just keep it at level 1, or go ALL OUT.
Ability 2 makes this skill more and more dangerous as you go in to a higher level. Because failure rate is massive without Befriend Pluto, you will constantly summon high level hunters that will attack you. HUNTERS SUCK ASS.
This is pretty much why Witches should try to avoid skills that they don't have masteries in. Its because
1. They come with a status debuff which only works if you keep leveling it.
2. They bite you in the ass if it fails, and failure happens a lot without befriend maxed.
Having 1 point in Flyswatter is fine. But no more. Unless you decide to become a dark build.
Also, Shururu should stay at level 5 until the Witch update patch. For now, he is terribly useless, and Jackyl's explosion is something you actually want asap, so keep him as weak as possible.
Once the Witch update patch comes out, you can detonate him whenever you want, so his high hp at higher levels don't matter. Also, with the patch he'll gain the ability to attract champion and boss level enemies at level 10 and 15. AND his enemy magic defense debuff becomes about 1500 points more powerful. So save your SP until then.
I was planning on keeping Flyswatter at 1, so no problems with that. Auto-detonation sounds awesome...
So this would be what my build would look like at level 50 I guess?
AradSociety - Skill Planner
And this is a Level 60 Build I did with the Shuuru patch:
AradSociety - Skill Planner