I agree they shouldn't stick to repeating the same stale thing over and over, but in addition to dropping the 3rd dungeon - the other 2 have become increasingly uninspired. Dungeons are a big thing in MMO's and they don't all have to be the same thing. So I don't agree with taking resources away from dungeons, I'd agree with putting resources in it to make each one more unique in style, substance and flow. The last time I enjoyed a dungeon on release was Keeper of the Lake, Amdapor Hard and Wanderers Hard. I enjoyed all 3 of these. I've really, really, really hated Dusk Vigil, The Aery, Sohm Al, The Vault, Gubal Library, Fractals, Arboretum. I dislike Neverreap, Aetherochemical, Antitower and Lost City hard.
That said, I want dungeons that are like none of the above that add some mix to how it works. The devs have, for whatever reason, so few resources. They keep spreading them so thin that instead of making a few pieces of quality content, they are making loads of really bad content. Quality over quantity.
As for sticking to the same template. I agree, they need to branch out. However, the design team has showed that they are incapable of designing interesting content outside of their core. So, maybe they need to stick to their strengths.