Why..

[azurerogue]

No it doesn't. The 5 hits from meteor storm are not 1 second each - they all happen within one second - so you're getting hit much more often from several wizards spamming MS than you are from one SG in the same amount of time. This is due to the fact that Storm Gust is a ground-target, persistent spell. This is exemplified by the fact that, if you cast fast enough, you can actually Ganbantein a Storm Gust and that 3x3 area will not take anymore damage until the spell is recast. Meteor Storm is also a ground-target spell, but it is an instant one. That is to say that once the meteor hits the ground it is no longer occupying those cells anymore, meaning more meteors can fall on the same spot before a full second is up if there are enough wizards spamming. You could also have meteors fall in this diagram:

Code:

[size=large]
XXXXXXX
XXXXXXX
XMXXMXX
XXXOXMX
XXMXXXX
XXXXXXX
XXXXXXX
[/size]

M= Meteor
X= Spell Range
O= Target Cell for Casting / Player being hit

Because of how Meteor Storm works, with several bragi'd wizards casting you could have all of those meteors hit at the exact same time (and you could easily have more). Since each individual meteor hits a 7*7 area around it, you're EASILY being hit by 4 meteors at once for a total of 2000% MATK in one second. Consider the significantly more painful scenario below:

Code:

[size=large]
XXXXXXX
XMXMXXX
XMXXMXX
MXXOXMX
XXMXMXX
XMXXXXX
XXXMXXX
[/size]

For the record, with a good Bragi this situation could easily be pulled off by having 3 or four wizards. Now you're taking damage from 10 meteors all at once. That's 5000% MATK in one second and it will just keep going. Perhaps MS is beginning to hurt a bit more than SG now?