Weakest/Hardest classes to PvE with

proph only skills on you + heroes, go monk. Heal, no smite. Judging by his avatar I would say his first char was a monk

To be very honest, atm, I think the weaker class is Ranger or Ritualist..not so much in PvE NM, but HM. Rangers re like, jack of all trades, master of none. I'm not saying Rangers are bad. I'm just saying, compared to all the other professions, Rangers arent the strongest option. disclaimer: i'm not takin pve only skills in account

I think BHA would disagree. Apart from PvE skills it's a very good (and only) option to daze monks, who especially in Hm are not an easy catch for interrupting with mesmer interrupts (or bow interupts for that matter).

I personally think mesmers are the hardest class to play. It's very difficult to make yourself useful. Interrupts i think rangers do better because they can interrupt more often. Ele's do the damage, together with necro's if they are specced to it. Warriors tank, and monks heal. A mesmer can slow doen (ele's water magic), interrupt (rangers bow) or shutdown (no counter from other classes) and degen/e-denial which i both don't value in pve, with L30 mobs and as it seems nonstop energy. Though, a good mesmer with a build suited to the situation can be very usefull if played by an experienced player. Ineptitude-based builds can be nice, though i might opt for a blinding surge ele/anti-melee necro.
I would say even rit and para are quite 'easy' to play, since you have a very clear task. As a rit or paragon you either healsupport or dmgsupport (imo same, since it's mostly the same attributerange). Not necessarily usefull but not hard to do. Again, I'm not taking pve skills into account here, so things like mobilespirits or imbagon don't apply here.

An easy class imo to start with is necro or ranger. They don't have the MOST important tasks in a group, but still are useful. Warrior seems easy but a team stands or falls with a good frontliner. Monks same. Necromancers Minions or curses are very usefull, but if you suck at it or need to get the hang of the class, your party won't die (unless you really are bad, but then any class is hard). Same with rangers, but instead of being useful when you are bad, you are more survivable and therefore can prevent a partywhipe (if you have a res).

Rangers may seem 'bad' to tards who can't look beyond OP PvE gimmick skills, but they can be crucial to the party's survival by interrupting/dazing the mobs' main nukers or healers. Playing Ranger correctly in PvE wouldn't make things all that difficult for you at all. Some of the more ridiculous groups you'd usually end up trying to over-power and out-heal would go down more easily with dazed healers and nukers. /agreed - there is a huge difference between a good ranger and a bad one, and hard mode only emphasizes the need for proper shutdown of a nuker or healer.

Probably the most difficult profession would be a Ritualist in HM. As previously said, Spawning Power is not incredibly useful to begin with and coupled with the fact that spirits are low level, and you find your options for HM looking rather bleak.

Its nice to see people trying to do things themselves to make the game fun rather than just whining at Anet. Good luck and my the Gods be with you.