Noob here. Is a ranger/monk viable?

Yes, Get your pet stalker in Pre to use as a tank.

Stay until you get Legendary Defender of Ascalon title

It depends on what you want to do with it. There are thousands of skills in this game. A profession combination alone tells you nothing about whether a character will be effective or not. As a general rule though, remember that you're not picking two professions, you're picking a primary and a secondary. Your primary defines what your character is and then you use your secondary to grab a particular skill or two to round out your build. As an example, a Warrior might go /Elementalist for Conjure Flame to boost their weapon damage, while a Monk might go /Elementalist for Glyph of Lesser Energy to reduce the cost of their expensive protection spells. If you were thinking R/Mo so that you can have strong ranged damage and be a competent party healer, you'll just end up being bad at both roles.

That said, there are builds where the secondary profession plays a starring role, but that's specifically by design rather than trying to be two things at once or forcing a square peg into a round hole.

Also, note that you'll eventually unlock the ability to change your secondary whenever you're in an outpost, though that'll be most of the way through the campaign in Prophecies.

Are you playing in Pre-Searing or adventuring to Post-Searing?

Pre-Searing everything should feel powerful after a couple of levels. Make sure you're putting your Attribute points into certain Attributes and not spreading them across all at the start.

For example I wouldn't bother putting any attribute points into the Secondary Profession unless you know you have a specific need for one of the skills. Rangers have good Armor and Healing themeselves without needing Monk skills.

Starting in Prophecies can feel a little weak for every class. The skills aren't the greatest and you can leave Pre-Searing at a level that was very strong in Pre and not so strong in Post-Searing.

Make sure you're getting the materials to upgrade your Armor which can be done in Ascalon from the Armor Crafters - make sure to pick the one with the Higher Armor Level as there are two.

You can still get Skills from the Skill Trainer in Ascalon but also look for side-quests which reward other Skills.

Overall Prophecies is slow and offers lower rewards than other campaigns. If you have the other Campaigns I'd suggest trying one of them out as an alternative.

If you are still in Pre, I have a couple of perma pre toons there.

Im an EST player usually on early am's if you want a hand