That's not horrible. I think it's fairly good progression for someone new to the game (which I am going to assume you are). It all depends on what your end goals are and if you have people who are expecting you to level quickly to help them out or not. Honestly, I prefer to enjoy the game and do the quest chains, gain rep as I go, read some of the story, and just have fun. I don't like it when WoW becomes a job. :P I already have one of those.
And I shouldn't spend much time in this thread, you guys will make me want to play again! And for those curious, I have a 70 Undead Priest on Bloodscalp, and a smattering of alts on other realms and on Bloodscalp, but no other 70s, even though I've played for over 3 years. XD
Still.. 3 days /played at level 26 is a good pace. It'll become a bit more of a grind as you get closer to the 40s, and the instances in that level range get tedious and no one wants to run them (think Maraudon, Uldaman, Gnomeregan). You might be fortunate to get a good PUG, but I'd look into finding a guild that's willing to help you out some if you haven't already.