I started playing today, and i have really enjoyed it so far. My only issue are those darn magma dudes. The orange dudes with high health, high damage capabilties, who are also fairly unaffected by knockdowns.  I was able to make one self detonate once, but i have not been able to replicate that since. How do i deal with those dudes?

Yeah those guys are a pain and you only encounter them in the beginning. Hit and dash away. when they start chasing you is when you want to keep dashing.

Be sure to lock onto those guys and dodge a lot.  I usually dish out three or four hits and dodge, three or four hits and dodge.  Locking on is key though to keep the camera on the enemy.