I see the reason you did it , but keep in mind you ruin the summon feature!
Example. Let's say I want to kill a boss in fog lower (ember) or in Zaken's ship or in TOI (TOI 7 for example).
My party and I are forced to walk ALL THE WAY (In x150 server , in 2018) in order to kill it.
On the other hand , I could have a summoner (DC) summon the whole group just by using Gate.And yes... when you want to farm more than 1 boss , it's kind of hillarious to be forced to walk all the way .
If you want to prevent "leaving" a summoner on the Quest room in 4sep , Make the Whole IT a location that you cannot summon from!
It's totally stupid to prevent me from summoning a party member near a normal boss!
It's not like every boss is near the Area's Spawn and You cannot have every single party member be Nobl (so that you can use nobl TP's , which doesnt even solve the problem ) at the start of the server.
Just think about it.