Add members in 24-man raid

I don't know if it's a bug, but it can be very annoying when I'm the current party leader of party A in a raid alliance:

http://i1078.photobucket.com/albums/...psdhbkeaav.jpg

Considering you can't interact or better said, tell the DF to not add members unlike non 24-man duties, the pop up of this screen is pointless and annoying. In the event where you have the classic wipe with people leaving, and being leader of the party, this screen keeps popping up after each new player has joined and the party is still being filled.
What is the point of this pop up? It also has priority over any ready checks or notices, having to tap back in to whatever has popped beyond the add-members-popup.
Any plans on adressing this?

Don't worry. All party leaders of all three parties in a 24-man-raid get this message. The first who clicks decides what to do.
This pop-up asks just if you want the DF to search for a member of an open slot anywhere in your alliance it's not just in your party. it will pop up every time any player leaves/get kicked from the duty and a slot opens anywhere in the whole alliance.

For your screenshot as example it pops up because a member left Alliance C, system recognized there is a open slot and asks all party leaders "should i search for a player/s who can take this slot/s or shouldn't I?".
If you say "yes" someone you wants to join a duty in progress will get a slot and join your duty. if you say "cancel" you will never see any replenishment to your parties.

I can see why this can be annoying in scenarios where people join and instant leave.
They could just make it that DF will always search for replenishments without asking for it...

But, will it actually NOT replenish if all leaders cancel? I didn't think it would.

Only the first input counts.
If one (the first) leader says "Yes" it will replenish. If he says "cancel" it won't.

iirc you can activate the replenishment manually in the DF again if it was canceled.