Torn between storylines... Need Advice

I mostly solo, and at this point I have a level 15 Warrior Monk in Lion's Arch.

Then I bought the trilogy so I had access to all GW content now (including Eotn). I now have MOX and the 1st two EOTN heros, but EOTN is proving to be too difficult for me.

Now to the question... Being in Lion's Arch, I have the option of splitting off into the other 3 campaigns, but I want to maintain a cohesive storyline and I am interested in doing ALL of the quests so... Should I continue on with Prophecies? Or split and do Factions or Nightfall?

I hear Factions will solve my money problems as my 50AL armor is only half runed. And Nightfall will add some more heroes, but I seem to be doing ok with MOX, Ogden and Vekk.

Any suggestions? Logical progression? etc...?

Prophecies is glacially slow, and once you create extra characters and get through it a few times it'll start just feeling long and boring, but it's a great campaign for starters. It moves along just fast enough for you to keep up and it's the easiest campaign available.

I'd recommend you work finish that first just to get the hang of playing the game. Then move on to Nightfall. As far as I'm concerned Factions might not even exist.

You can also do a shortcut regarding armor. In Lions Arch you can pick up the quests and get to Nightfall or Factions where you can purchase maxed armor quite easily.
You can do that as soon as you can afford and then go back to Prophecies and move on with the storyline. You should look out for all quests that give skills as reward, the others you can skip or delay as you please.
If you like storyline I strongly recommend finishing each campaign in order, that is Prophecies, then Factions, Nightfal and EOTN last.
Although you get a "newbie" boost in EOTN making you equal to a lvl20 it is still no beginner campaign. The enemies there are more complex, and often packed in mobs with better skills that makes them harder to beat than mobs in the other areas.
Once you have done most or all in the other campaigns you will have some experience and heroes and can handle EOTN better.
Good luck on your hunt

Go on with Prophecies, your 3 heroes will be more than enough to help you through. If you find you have some armor problem, you can quickly jump to kaineng city to craft a max level armor (be prepared to spend a lot of money on materials though).

However, if you really want to feel the real prophecies atmosphere...don't use any hero!

Thanks for the feedback!

I think I'll go ahead with prophecies then... Although unless there is a specific reason to take my prohpecies hero through Nightfall and Factions, should I just create a character in those campaigns to go through? Or is it beneficial to a prophecies character?

Take your original character through all the campaigns - you will be able to travel to all the towns, find armor and skills that you can have only after you finish quests and fight monsters from those lands - for a new player is pretty cool to see everything around with only one character and be able to fast travel everywhere if you need an item, or skill or anything that would help you later to get the runes and insignias for a good armor or the parts for a specific weapon, stuff to help you in pvp or dungeons, or elite missions.

Play with one, main character through the whole game. If you feel that warrior is not your ideal (remember that the /monk part can be changed later), it's time to roll another character now.
If you're interested in the lore, want a cohesive story and expect some sort of challenge from the game, stick to Prophecies for now. Don't even visit other continents for now. The campaigns are kinda connected in the story, in the end, so keep Proph -> Factions -> NF -> EotN order. If you don't care about the lore, starting with NF will bring you more useful heroes and, especially for a beginner, better weapons - mostly due to the ease of modifying them.
I kept the original order - haven't even bought the next part before i completed the previous one - and i'm quite content with that choice.