Allright here we go:
GUILDWARS: this game is cool because the dudes hwo made it announced a suposed balanced playing style and bladibla... Anyway, despite many people say otherwise, PvE is easy. there is no way arround it! Therefore, any 2 classes you may choose will synchronise relatively easy.
But, imo, the class that have been suffering more handicaps in pve are the elementalists, since the different mobs have high armor vs the elemental dmg (witch can be surrounded by some cool skills and a diferent playstyle that many people are not used in this game.
So, imo, even if both of you choose to play elementalists you can stiull beat all 3 campains with no major problems.... all this because pve its easy...GUILDWARS is not about pve. GUILDWARS is about pvp (or should be all about it, or even the name of this game for it self does not make any sense at all).
Many people can tell you Dervishes cannot make big D0mg...thats a HUGE lie! In fact, a general wounding strike build with some tweaks and an OoV necro with some special smite skills can make dmg as some people cant even imagine (yeah, because theyr mind is formated to play Discordway...but thats other issues....)
Sins are weak because no armor no big d0mg no nothing...Again a big lie!!!!
Rits....no comments!
Necros....lol
Monks had always find theyr place in pve in general so yeah....
warriors ---ยป WAMMO ftw!! lol joking :P Serioully now, good old warriors have always theyr utilities. The only handicap i find for this is when you play some warrior builds with endure pain, healing breeze and some other bullshit skills you may find arround. Good old hammers with good ROJ (yes RoJ was nerfed but can still be used) Monks or with some other warriors and a MoP spiker can do a Big d0mg and incredibly can beat you the game w/o big problems if you do some obvious tweaks along your journeys.
Paragons: add a MoP nec and yuou have a strong spike build combined with the support power from paragons ith is incredibly usefull for monks. Handicaps...? I dont see any, unless you play paragon rlly bad or unless you have some bad team build in witch you just trow in those paragons (or paragon)
Mesmers....lol mesmer is so fun in pve...you can play w/e you want with them. In fact if u want a good chalange try to bring those mesmers to the front line (Illusionary weapon does nice dmg) and suport them nicely with some power midline. Its possible to beat the game if you do the necessary tweaks along your adventures. its not hard!
have fun!