Battles between Magicians differ slightly from that with other classes.
The major difference, being high-level spells, would rarely be used in a one-on-one Magician duel.
The reason was simple. The higher the spell level, the more complex its spell structure. Magicians would then have to spend longer time on both constructing the magic and gathering enough energy to release the attack, inevitably increasing the time needed to cast spells.
This was almost an iron-clad rule.
A Magician had to be extremely focused during spellcasting and would be vulnerable to any incoming attacks. In most cases, Level-1 Spells would be more than sufficient to defeat the opponent, which was why Magicians rarely used high-level spells when they were not under protection.
The most commonly used spells in duels are Level-0 and Level-1 Spells, Level-2 Spells would also occasionally be used either for ambush attacks or when a lead had already been secured.