The arena matches can be pretty much anyone. I wouldn't recommend doing it too much until you got a at least one +10. Magic can indeed be very powerful. I have a character that is 100% magic other than smacking people with my staff (which works surprisingly well, no one sees it coming). Having played that character for an extending time it all becomes about switching my spells to try and catch the player off guard with something he doesnt see coming. Like I can use great combustion a few times he will try to roll behind me but I hit him with the flame whip. Or using a flame tempest that makes them fall back, dark orb while in cover to try and sneak a hit in. Switching between heavy soul arrows (or homing) and normal casting ones to try and get someone in between rolls. Next time he sees the fire channeling move he assumes tempest and tries to just get out of the way but I send a flame snake that hunts him down perfectly. I'm really stressing how much you need to fake out your opponent because at a certain level some people just become almost entirely immune to magic. If you focus on dodging magic and just keep an eye on him, dont do anything reckless, and just dodge his spells you will get into his head. Most of their spells are on a limited supply so the longer you draw the fight the better. They will almost gurenteed try some weird mix of spells like I said earlier to try and get you to dodge too early or too late. Of course there are some people that only spam the one spell. I find the best way to get good at fighting casters is to try it yourself. You'll see how other people go about fighting them and will find the limitations in spell casting that you don't really get too familiar when you're on the other side. Pretty much every spell can be dodged if you know what you're doing. Try rolling into the homing spells and under them, when you try to go side to side it turns and will probably get you at the end of the roll.