I guess it depends on who you are. I find getting the 50 kills in WvW to be rather easy, for the reasons that the poster stated.
However, Fractals are 'Impossible' for me to get. Why? Because I won't step inside them. Or dungeons. So they will never get done.
Love doing event counts. The jumping puzzle is a neat one (seems like I get 2 a day for doing the WvW one I like to do with 2 characters, and there are other easy ones I can do alone.
I'm just crossing my fingers they move to a grab bag method, where you are given the option of maybe 10 things and have to complete 4. Gatherings, rezzing, things that are simple, or maybe boring, for PvE folks to do. I personally don't mind the WvW one at all, as I find it fun, but not being a PvP person myself (which is odd, but I don't see WvW as PvP, per se), I can understand why people might not like that. I also can see why people might not like dungeons and fractals (which is the same thing), because I don't. And last I checked, I'm people.
So for me, I'd much rather do the WvW kills, the DEs and the new puzzle one are fine, and then for my forth, let me gather or sell 'n' things on the trade post, or something else. But no dungeon-y things for me, thank you.
If you are just going for world completion to get your Gifts of Exploration, all you need is each map complete. Hearts, skill points, points of interest, and vistas will complete world (don't forget you also need WvW maps).
What is the difference between the two? What you talk about in the first paragraph and the second paragraph? There's a super-world explorer completion achievement beyond making World Completion go to 100%?
I just got my WvW stuff done today (yay!) and was going to get back on the rest, slowly. I'm only at 54%, but I'm not in a terrible hurry, still have a lot of crafting to do as well, and enjoy other things in the game.
But I wasn't aware there was something to explore 'beyond' getting that 100%?