You people play the game WRONG, yes you do!
Lets say this, all parties i came across are usually some random mix from allways complete different proffessions,
sure you have some hard time to complete dungeons (on lower levels),
or get OPd in WvW,
HERE IS THE SOLUTION FOR ALL YOUR PROBLEMS!
make party-groups ONLY and i mean it ONLY of the same proffession as you are!
Now.. imagine,
WvW a party of 5 Thieves with Critical-Power Build,
you stealth your group, run inside of a zerg pop up AT THE SAME TIME in the middle of your enemie with your Elite Skill: Dagger Storm
… guess what happens 
Now.. imagine,
a group of 5 Guardians with they stacking buffs and group healing ability… in dungeons..
(yes would take a bit long) but you would make out of every dungeon with the count of 0 deads for sure
Now.. imagine,
a group of 5 Engineers defending a camp in wvw with the amount of turrets they can create together in a circle of dead,
or fighting a boss while having only imobilize turrets up …
:)
Now.. imagine,
a group of mesmers in pvp (try to find people who look even like you lol)
… boy and now look at the usual mixed parties where the most of the people dont even know what those buffs of other proffessions do and walk right out of them and die ^^’
(edited by Amen.2630)