Firstly the story varies massively depending on the chosen race, order and minor race.
For example you chose Sylvari and the 'Act with wisdom, but act' storyline correct? Well in this story you meet Trahearne early on, you meet Carys and Tegwen early on (they show up in a later step) and your story is somewhat focussed or Orr and the Risen.
But if you had picked Norn/Charr and Vigil you basically don't really ever deal with the Risen until Claw Island where you are suddenly taking back seat to this loner Sylvari rather than a superior.
Aside from some of the actual "missions" just being flat out annoying or worse, boring the story suffers from some pretty serious flaws:
The story jumps around between being a 'serious fantasy' story, to a light-hearted comedy and slightly dark almost horror tone just whenever and for no apparent reason.
You're rushed through the racial and order prologues, both of which are actually quite fun, just as you feel like you're getting in to them.
Then the real story starts with a bang when Claw Island and Lion's Arch are captured by the Risen but after that you're basically just slogging through Risen and Risen Krait with lots of little short term goals that aren't ever really cohesively put together.
Sooooo many characters. The game throws new characters at you every story step and there's absolutely know way to know who is important and who will show up later on. Hilariously you can get right to the step where you [spoiler](kill the eye of Zhaitan and cleanse Orr) and you look at your friends and think 'Who the hell is that?'.
The cast should've been far smaller than it was and the important characters should've been more prominent. Trahearne, Laranthir and the Pale Reavers for example should've been omnipresent; every time you dealt with a Risen problem you should've been running into them.
Destiny's Edge should've been used as an example of joining forces and working together to overcome bigger challenges throughout. I mean, that's supposed to be the theme of Guild Wars 2 but you wouldn't know it.
Places attacked and defended, magic/knowledge discovered and used, technologies invented and exploited et cetera et cetera.
These things happen at various times but if you aren't in the story step that it happens (and even if you are it doesn't necessarily mean it'll be explained) then you'll be in Orr and suddenly the Pact have some technology that just obliterates Risen easy peasy lemon squeezy; leaving you to wonder why the Risen are a problem in the first place.
To be honest you could go on for hours about the flaws in the personal story. The issue is that individually each part is kinda OK and mostly works but as one cohesive piece it's just a big mess of mushy blah.
I don't know why but I've always thought people said that Zhaitan just was or at least in the story felt like a thoughtless, mindless force of nature.
This is because during the development of Eye of the North right up until release ArenaNet constantly described the Elder Dragons as being mindless forces of nature. Now, perhaps this was their way of trying to set up a kind of mystery plot where we 'discover' that actually they aren't but if it was then the story does a terrible job of revealing this as it just seems to be taken for granted that they aren't mindless forces of nature (yet we are told by the writers of the story that they are...).