Its a double edged sword for me.

1. If I am in your game and you are running with a pro party and you are parking, I will probably laugh at you.

2. I have been in instances of elite maps with either pugs, with under geared people that are not experienced in elite, or people that do not use plat revives. These runs can go upwards of 40 minutes. Parking is good for these kinds of games where its just really not that possible or realistic to do it otherwise. I prefer to just kill everything up to the boss personally, but I will also run once the appropriate number are killed if others are going to (usually the case). But this isn't feasible for people that can't plat revive. In some maps, its near impossible to get back to the boss by yourself. And chances are... you are going to die.