That's what Anet has always done with Guild Wars. I never really played GW1 so I can't really compare the content of each expansion. I have a feeling each GW1 expansion had multitudes more content though.
Factions, the first expansion, was kinda poop, I think it was a lot smaller than the base game(which wasn't very big to begin with), but did add a bunch of pvp stuff(battlegrounds and shit) as well as 2 entire classes. Nightfall, the 2nd expansion, was larger than the base game and the first expansion combined, shit's like an entire game and added one of the best feature in the game, Heroes, which were way less shitty than mercenaries and added some sort of collection/team composition system to the game. Eye of the North was small, but had a lot of story stuff packed in so overall was fairly interesting, but didn't really add that much, no new class(only expansion without any), not many new skills. It was however the last expansion for a game that was already on its last legs and shit.
Overall the price tag was kinda high if you bought everything at release, but for the most part was worth it, especially Nightfall. Wether this expansion is worth the money or not though, don't know, not exactly sure how much actual content there is. There's a bunch of new specs for every classes and new weapons so that's nice but for a lot of people content is how long you can play new stuff and if there's only 2-3major zones, that's like a weekend worth of content which would be pretty crappy.
Good thing about this methodology however is you can just buy the shit later and enjoy the content for a lot cheaper. When I bought GW1, I got every expansion+base game for the price of one new game, and it had like several weeks worth of content.