Hi Xtensity,
To answer your questions, server population has gone down in the recent year or two. I'm not sure how it compared to when you played which was probably chapter 1 or chapter 2, but there were a lot of players during Chapter 3 and who quit in the middle of Chapter 4. There are no official numbers for it, but one way to kind of tell how many players your server has is when you log in, there is a player density or something like that which tells you whether the server is full (red), crowded (yellow), or light (green). I'm not sure if those are the exact terms, but you get the idea.
I think one of the reasons you can't find people to help you with your quests is because not a lot of people quest in the old zones now. You can now choose a 3rd class and there are two accompanying zones that allow you to level up your 3rd class very fast, so a lot of people have stopped going to the old zones like Dustdevil Canyon, Weeping Coast, Savage Lands, etc. I'm not sure what zone you're in, but that might be why. My advice to you if you want to quest and level up is to first check out what you might want to do for a 3rd class and then quest a bit in the 3rd class zones (Coast of Opportunity, Xaviera). There's a really good daily at the end of Xaviera that gives you 266 k xp per completion, and it only takes 2-3 minutes to complete.
Currently, there is no way to do a server transfer and I doubt there ever will be, because then you would run into a lot of problems. For example, what if a scammer scammed a ton of people on Artemis, got a bad reputation, and then transferred to Osha and started scamming again there.