Party members should be able to choose if they want to be teleported to the quest instance of other party member. You can implement the same mechanic like Diablo 3 where there will be a pop up with a countdown for players to decide if they want to go or stay and continue with what they are doing. As being teleported suddenly breaks the flow of the player and is very irritating.
This, sometimes a party is together just to share exp and may be in different areas of the map hitting different monsters or just taking a break and chatting, getting teleported across the map in the middle of things is a gigantic pain in the behind.
Guild Wars 2 also has a timer for the players in the party to choose if they want to enter the instance. I should also mention that I was in a party, but some friends were in the city while me and my bf were teleported to the same quests in another map and we decided to do that together. There was that part where we burn some carts blocking the way, we did that together while the other players were in town, and when they went for this quests, the way was not blocked anymore. I don’t think it was fair storywise for them, since we were apart.
I actually like this feature. Parties are for playing together but I see the reasoning that some people might have been taking a break, are talking or the like.
Let’s settle on this:
If the characters are close together (close enough as to share exp - you can see this on highlighted names in the list instead of greyed-out ones) and are not sitting then they are auto-teleported to the boss asumming, they are active. If they are out of reach (far away on the same map or other map) or are sitting then they should get a message: “Your Friend X needs help!” with an option to teleport and help or to refuse (with a counter of like 15-20 seconds).
Too complicated. The timer for everyone in the party seems way more reasonable.
It sounds complicated but in fact all the complexity happens in the background. The change to the current situation would be that people that are far away or are sitting wont be dragged in the battle but get the invite with the timer.
Well i understand wad Orchide means, but still i think a timer and a popup box asking players to choose is a better idea as imagine your friend have to attend to something and he/she forgets to put his/her character to sitting position and are then forced into the boss fight.
Well, they are right now (pulled into the fight) but not many complaining because most of the time it’s fun.
And if he/she forgets to sit … next time he/she will think about it for sure 
