Im currently level 58 and i'm midway through Zafaria. Would I be considered way underleveled? I've had a few people come up to me and tell me that I am. And if I am, what side quests would be suitable to help me reach my appropriate level.
If you are a high enough level to get to Zafaria, then you are just fine. That means you met the requirements. Just work on quests and ignore what other say.
Although it's not really required, I think you should go do some side quests. I recommend doing Wintertusk, if you haven't already; it gives SO much exp and will help you in the later worlds greatly. If you can't access Wintertusk, then you'll need to complete all of Grizzleheim first.
Ehh... I would go and do some side quests, if you haven't already, definitely do Wintertusk, it gives a lot of exp and leads to new spells and a pet quest. A lot more difficult enemies will be coming up soon, so you wanna be ready.
If you're struggling with almost every battle and staggering out of the ring with barely any health left ... then you might be underleveled.
On the other hand, if you're doing fine and can solo most battles without too much stress, then you're at the perfect level for your skills. Knowing how to stack blades and traps, for example, can make battles go smoothly even if you're lower level than what is typical for that world.
Basically, if you feel you're underleveled then you might be; but if you feel like you're doing fine then you probably are fine, no matter what other people think.