30 minute cooldown makes sense,
my fleet was grinding only one mission over and over again on Tribble because the guys think it has the best fleetmarks per hour ratio (which i don't really agree with)

this will force us all to do a few different ones in rotation.


...the bad thing is, if you drop out of your group for whatever reason, do a PUG mission in the meantime and try to reconnect with your fleet group later you may have problems doing so because of the cooldowns. Oh well i guess we all have multiple chars to hop around.