No, I am not saying remove the cool down and I am actually not saying remove or reduce the cool down on all "daily" missions.
The TLDR version:
Any "daily" mission that only rewards dilithium and skill points should have its cool down period reduced to 30 minutes or an hour. This would NOT include the Investigate Officer Reports mission (Fleet marks), or the Distress Call mission (which gives out items to access another mission), or any others that give out item mission rewards. Please note, I am not talking about item drops, just the rewards you get when completing the mission.
I am sure that the cool down made some sort of sense back when most of these missions gave out emblems, since there wasn't a daily limit on how many emblems you could earn per day. However, now they all give out dilithium, and there is a hard cap of 8,000 dilithium per day, so even if we earn more than that, we can't get any more than that a day. So there is little economic reason to put two limits on this.
Also, it does not make sense compared to other dilithium giving missions in the game. Both normal and elite STFs give dilithium, and they only have a cool down of an hour.
Finally, I do not see a reason for any player to be limited on how they play the game. If someone wants to run between the Defari dailies all the time, I see no reason for them not to. This is pretty much the same as someone running STFs all the time, which people do. It also fits in with other similar missions, like the fleet mark missions, all of which have a much shorter cool down that the 20 hour dailies.
In conclusion, as there seems to be no reason to have the 20 hour cool down on these missions, a few reason for, I would again like to request that these missions have the 20 hour cool down changed into something that matches the other cool down missions in the game.