I am going to use Wow as a reference point here, not because I think it should be the measure of all things MMO, but simply because I have played it before and know it well. So, what are the points that scream “different”?
Experience distribution between different kinds of activity.
It looks like killing mobs is literally the worst possible source of xp in GW2 (it is as if the game wasn’t about killing every living (undead, mechanical, elemental) thing in your reach – crazy, I know). In WoW, the ratio of xp given for a level-appropriate kill (rested) and a level appropriate quest was about 1:15, and between a kill and discovering a part of the map or gathering a resource node it was more like 1:1. In GW2, gathering a node gives about 3x, discovering a waypoint or a new area 10-20x, doing an event about 50x, and doing a regular area objective (a heart) more than 100x as much xp as a single kill! Seriously, around level 10 you would get 10-something xp for every scalp in your collection (granted sometimes there is a bonus for a kill streak.. 20 points or so), and over a thousand for completing a heart. So running around exploring and completing whatever the map has to offer is THE way to level – combat is not quite optional, but you don’t have to spend all of your game time hammering mobs. Besides, you can avoid at least most melee hostiles, because
You enter combat state upon taking damage, not upon taking aggro.
And the mobs don’t necessarily outrun you. Besides, they don’t get that one free bite when they are first dashing towards you (WoW has a considerable – split second, but given the effect I still call it considerable – lag displaying a player’s position to another player. There was that time when I was running two copies of the client back to back, and when one character was riding with the other one on /follow, the “follower” client was displaying the follower right behind the leader, while the “leader” saw the follower so far back that at least two more riders could fit between them. And that one free bite thing, when any wildlife specimen who has taken issue with you riding through its neighborhood can bite you once on its first attack even though you were quite clearly never in melee range? I think it is the same lag, now between you and the server itself. How PvP is even possible in this game is beyond me.)
Mobs that you are running into head first would still get this half second of sprinting right past you towards the position you occupied a second before. Annoying when you are a melee class.