No, you don't HAVE to. I've seen blades and assassins manage, and there is usually a normal mage for aura. It is just much much easier when the water dragons don't instantly kill you on a direct hit. Everyone has access to the event version of the pirate sp though, they give it out for free every pirate event so I don't see why you wouldn't use it. It is a percent damage raid so it isn't like using different sps would really be beneficial at all.
If I'm hosting a raid though, as a member of MY raids you do have to use appropriate pet/partners. That means as long as your level is high enough to catch an imp you are going to use a ranged magic pet, and if you have a magic partner you are using that as well. I will literally wait until every last member has their appropriate pets, and if you don't have an imp but are able to catch one I will walk you over to temple fernon personally and have you catch one before we start xD
So if you think people telling you to use pirate sp is bad they are letting you off easy.
I'm pretty sure they do the same damage as pirate, though I believe you are referencing Halloween raid? Even in snowman raid pyjama doesnt do more damage, these effects are stated in the events info though if people want to dig around for it.