Hunters a great first class to level as assuming you go to the end then play some alt's the Hunter is by far and away the fastest to get around class and quickest to do a little ore/wood/leather farming for crafts and for a little cash so its a great alt to have to make your next alts easier. Pop on your hunter, port to the right place, get some leather and make them some armour, or give them some gold to buy weapons.
I wouldn't say any class is easier or harder than any other, realistically its never hard to play MMO's or use your skills. Hunters simply the best to do first because of travel powers and quick killing ability.
Taken a month or so off after playing for a month after the expansion, its a very good expansion with lots to do but the 2 new classes felt like a massive letdown to me. The Glass cannon caster is horrible to play through early levels IMHO, its supposed to get massively stronger after a while but I was bored getting there. Warden, its nice in theory lots of alternate moves to use, but in reality the choice of moves didn't provide much difference, I could use any combo's and really felt like I had similar survivability/damage output. If you try those two I'd leave them till last.
MIncers/burglars were great fun pre-expansion and were a little poo after, though theres always balancing issues and I'm sure at some point they'll be fun again.
Loads of people play, very rarely do you have to solo, likewise should you wish to solo you won't be overly crowded and having people stealing your kills constantly due to silly numbers of people doing the same quests.