There are also a lot of zones for multiple levels. Each race has their own starter zone, and there are several zones for each range of levels. You don't have to go to each zone, but if you don't you'll be missing out on story, events, skill challenges, ranger pets, etc.
There's also different kinds of difficulty. If you're good at dodging and avoiding damage, the game will probably seem very easy. Ranged characters also have a slight advantage over melee characters, but it's really only noticeable in large events or against large bosses that throw down one hit kill attacks with little warning (something they've said they're working on).
The highest lvl character I got during the bwe's was a lvl 18 guardian, and one thing I noticed was that lower levels (1-10) were pretty hard because you don't have access to all of your tools and there's often little margin for error in dodging big attacks. Around lvl 12-13 that started to change as I had access to utility skills, weapon swaps, etc. that allowed me to mount a more proactive defense.
Another thing, some events become ridiculously easy given enough people participating in them, even despite scaling. Others are challenging no matter how many people seem to be around. I think there's still a lot of fine tuning going on.