I would note that one does not hold a spear at its terminus. So, a 3m weapon reach is out of the question, I would say 2m at most. Add on about 1m of personal reach, and his enemies are not within melee range. Even if you assume a 4m reach, his enemies can stand 4.1m away from him and (assuming a 1m reach plus 0.1m long weapon) and beat on the fortress. The spell is best used with a missile weapon, or to counter missiles while you beat on the brutes.
Now, a clever warrior would spell master the spell to create a 1m radius. Then, as long as the warrior's weapon is at least 1m longer than his enemy's weapon, he can get an attack off. Even in this case, I would make the warrior suffer a penalty because his enemies can dart in and out of melee range. (Then, I would allow the warrior to learn a combat maneuver to offset the penalty. It's a good tactic, but it should require some DP to pull off consistently.)