how can Sylph's "kick some fucking ass easily"?

Have you read any part of Homestuck with Kanaya in it? What a babe. Or what Aranea did to Jake? Sylphs are part of the Creator Pair. Sure, they Heal- But they also Improve, Increase and Make. Creation is within their realm, they Make people do things and Make things themselves, buff others and themselves for combat, and have generally proven to be able to fuck shit up when they need to.