[Bozos of Bones]

Firstoff, whoever told you a Mo/W sucked and that you should switch to W/Mo is a person who's advice you should not heed. The W/Mo combination is the most laughed at because it's regarded as the "noob" class. The vast majority of characters you'll see frolicking around will be of the /Mo variety of the Warrior, and the very vast majority of those will act as proof against Darwin's theory of evolution.
The Warrior class will surprise with it's complexity, if you ever learn to do it well. I myself, after completing a Necro and a Mesmer, thought a Warrior's job was easy, so I started one to try it out. It is easy to just ram the mobs head first and then spam attack skills like mad, but then again, that approach hardly ever yields any mentionable results. In PvE, the Warrior's job is to primarily take damage and protect the squishy(caster armor) targets either by blocking the way, attracting attention or slowing the enemy down. However, unless you are running, NEVER equip Mending. I can't stress how important this is. The running joke right now is the Fiery Dragon Sword Mending Warrior/Monk with Strength of Honor. If such a character appears in your group, expect disaster.
The Monk, on the other hand, is a wholly different subject. If you choose to go smiting, always advise the group that you are smiting, so that they can tell you to change to healing or protection. On the rare occasion the group gets a monk, they don't want him to smite around. If you go along the way of the Healer, you'll find yourself looking at red(if you're lucky), green(a bit less lucky) and pink(much unlucky) health bars of your allies, and make sure that the dark red area is the smallest possible. This can be tedious and boring. The Protector, on the other hand, has to look over the battlefield, and take note of who is attacked by who, and act with that in mind. No matter which way you go, expect to be praised, cussed at, lifted in towards the heavens and stomped in the mud by most groups, depending of you doing a good job and them knowing it, or you doing a good job but them sucking it regardlessly.
Now, a bit about primaries and secondaries. The primary you choose you can NEVER change(unless you make a new character), whereas you can change your secondary later(final 20% of the storyline), and change it back any time you want. You miss out on your secondaries primary attribute(Strength, Fast Casting, Divine Favor, Energy Storage, Expertise and Soul Reaping) and you can only apply runes to the matching class armor, and you can only wear your primary class' armor. There will be people who will tell you that some classes are not meant to be primaries, but secondaries. These classes often include Mesmers, Necromancers and Rangers. Ignore these people to the best of your ability.
@ T-D-C: Where do you get stopped in a Droknar run? I can make it all the way once I get throug Lornar's, but the Golems always stop me very close to the exit.