Player returning after a few years? Please help.

Well, I use to play GW about 2 years ago... and I have a few level 20's... I have a Warrior/ Monk, Dervish/Monk, and a Ele/Mesmer that is level 16. I also have a few level 5's, etc... Well, I came back recently, and I basically lost all my knowledge of the game... I wasn't the most experienced player. Well now, I want to come back and get pretty good in the game, good character, spend some time on him. I have the first 3 campaigns, not eye of the north. I would like to buy that one, and carry and character through it... I was thinking of making an Assasin, are they still good? I remember they could SF and solo UW... I enjoyed my Warrior, I'm just not sure if Monk was the best Secondary.... I hear ritualists are good, but you don't get a lot of action. Are Derv/Monk's still good? I'm just wondering what character I should make, and what is a good overall character. I enjoyed my ele, but he was just so squishy.... Can someone give me a rundown of what is/isn't so hot nowadays... I just want to create a character to run through the game and go to eye of the north, farm, etc... I don't plan on making a running character, and not a huge PVPer, but would like a overall decent character... Please let me know. Thank you!

Ritualists are pretty good right now with DwG and farming Domain of Anguish for Gems.
Assassins are mainly used in speed clears and tanking. UW you aren't able to solo anymore and they added a new end boss in UW that is called Dhuum. There are speed clears for UW that take under 30 minutes.
I would suggest ritualist simply because it's really easy to go through any campaign with them without any help.

Ritualist is by far the easiest character atm with SoS, but I don't know how long that will last, seems like it needs a nerf, just like DwG, but we can see how long that took with SF, just might aswell enjoy if for a while ^^

But I get the idea you are more of an melee kind of person. Dervish isn't very great, but awaits a buff the next update (or maybe the update after that ) which might make that a better profession then it is now. I quite see it happen that it gets involved in FoW and such, with Great Dwarf Weapon and Strenght and Honor, it could be quite strong. So if you dont want to start over a new character, I would go with dervish, invest in the still unknown, otherwise go for Ritualist.

But important is, the game is very well playable with every profession in the game, just some more then others. Just see what you like playing best, and invest your time in that

Actually ANet reps (here on Guru) have confirmed that Dervs have first priority because they have already worked out what changes they will make. They are just hammering out the final tweaks and are testing.
SF sins have been nerfed, but are still welcome as main tanks in most areas.
As everyone said, DwG is flavor of the month but calls for a nerf are getting louder despite that they only see heavy use in DoA so far.

The biggest change is WiK (War in Kryta) which are missions against upgraded white mantle (multiclassed and tweaked to mess with meta builds).

If you want good advice, get your Derv up 100% for the upcoming changes. It's been confirmed that they are in line for some juicy buffs and you want to be ready to start abusing them in case they get OP'd and you'll only have a little time before rebalance.

just to throw this in there: yes ritualists are good for a number of reasons:
*spirit spamming (who doesn't like doing 100 armour ignoring damage through spirits?) some people say you just summon spirits and then wait, but since you have great energy renewal through siphon spirit you can do pretty much whatever you want while the spirits kill stuff.
*restoration magic- powerful healing, and more interesting methods of healing (than monks imo ^^)
*farming/high end, yep rits are in demand now.

but to be honest if you wanna get in the PvE meta there are plenty of builds for all characters, but cons are mostly needed for high end areas.

Are Dervish/Monk's still good or are there a better secondary?

Warrior is the best secondary for Dervish I think. But remember, once you get ascended (that is after the quest Hunted! I think in Nightfall) you can change your secondary profession for the fee of 500g (that is only payed once for every profession, after that this secondary proffession will always remain available to you) in the Command Post (that is again, for Nightfall)

So when you want to run a build with Monk secondary and the next day with a Warrior secondary and the day after with a Paragon, that does not matter at all.

For strong builds, you can always look on PvX wiki, for guidelines on what is good, you can always create your own builds or give them your own twist ofcourse. I think this is atm the most popular Dervish build, but that might change after the next big update