No matter how short or fun it claims to be, as long as XP is given for killing mobs and a certain amount is required to advance each level, it's going to be a predictable grind to some extent. If players are in the situation of 'needing' to get a few (reputation) levels, the choice between staying in the one place to kill say 100 mobs or finding 5 events to complete (or just as bad, killing mobs while waiting for an event to begin), I think a surprising amount would opt for the former, especially on an alt. It's failing to change the mentality of killing mobs for advancement rather than compelling players to search for activity.
Levels and levelling is such a tired mechanic at this stage, that I was expecting something more innovative from Arenanet. While they have not discussed mob power or levels, there's a lot already in place or in the original that could have been developed leaving levels at the door. Look at the type of content a player could choose between on logging in for the evening, a choice of doing achievements, collecting skills and traits, participating in events or venturing into dungeons and killing bosses. They could reward attribute points for those activities and task the player with acquiring a certain number in whatever manner they want. Not such a big departure from levels, but even with this there is player choice and adaptability in choosing where to spend points first and a higher level character has a broader spread of attributes rather than vastly increased attributes.
What's most important is that they need to move away from incentivizing boring repetitive tasks, i.e. killing a mob and receiving a set amount of XP. Looking again at the activities I think should be rewarded:
1) Doing the daily achievements - random, dependable but hopefully skippable.
2) Collecting skills and traits - reward skill, knowledge and research about your profession.
3) Killing open-world and dungeon bosses, rewarding co-operation and providing challenge.
4) The Karma from events could also be used to buy attribute points, offered alongside the more material rewards. Tying character progression to events might frustrate some people, but it's not as dependable as some activities, and the rewards for a challenging or rare event could be significant to reward exploration.
The only thing keeping levels in play is being able to simply communicate the difficulty of mobs to players, which I think is an opportunity ripe for innovating.