Maybe true, but the Devs did say during one of their demo play throughs. Some of the people playing the game did not realize they were playing against the A.I and got upset (for lack of a better word) because of how good the AI was. So i think playing solo against the AI will be plenty of preparation for online, even if you start off at lvl 20.
Im aware of that, but having the AI pass as humans does not mean they are going to use the same strategies. Humans have trends and patterns, and don't always play logically. In general, a computer is going to go for the "best" strategy, while a skilled player may expect you to try and counter that strategy, and take counter-measures of their own.
A lot of high end play is figuring out what the enemy is doing with very limited information, and acting according to that, and I doubt it will be the same between PvNPC and PvP. It also includes misleading the enemy into thinking you're doing something in order to gain an advantage. I don't expect NPCs, no matter how advanced, to use such abstract play.