Players have been cheesing the effects of unravel when the seam opens by transitioning into a different area to avoid the initial 'blast' of seam sickness. I suggest applying the seam sickness to the wizard casting the spell immediately as well as to everyone in the area.
Its fine and anticipated.
The burst of Unravel is really very small. The entire area, afterwards, radiates high planar sickness. Entering the portal itself generates a much higher amount of planar sickness and that cannot be avoided if you hope to benefit from the spell.
Beyond that uses per day are the real limiting factor. The idea of planar sickness isn't to limit arcane magic so much as to make people hate you.