Depends on how fortunate you are with his Speed growth. If it isn't satisfactory, you can always boost it with Bonus Experience once he's capped Magic, Skill and Resistance, which doesn't take all that long.
Most of the magic users are on the slow side. Micaiah, Ilyana, Soren, Rhys and Bastian have mediocre to poor Speed growth. Micaiah and Soren will still become brilliant with clever Bonus Experience use and a little random growth luck. In many playthroughs I have capped every single one of Micaiah's stats, and usually about five or six of Soren's. Bastian isn't half bad either.
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