Janus Marius
Plo Koon Rulez!
How come one would strike the solo guy and then after that the other would? Why don't they get at opposite sides of the guy and then attack at the same time in different areas? Unless if you have a double sided blade/two blades, you can only escape by dodging one/both of the attacks, which would be much harder.
Actually, in both TPM and RotS, the Jedi end up flanking the Sith at one point or another. The difference is that both Sith managed to get out of the ugly situation before the hammering could commence. But a lot of lightsaber fighting is about predicting the next blow just as much as striking quickly; you'll notice that the Jedi duos always try to assist the attacks of their fellows as opposed to hitting quickly to overwhelm a defense. Part of this is common sense - trying to mesh two swinging lightsabers in a situation isn't easy. It's dangerous to all parties involved, and reckless hammering away could cause fatal mistakes.
It's very likely that the attacks we see are more the result of drills on complementing the abilities of one's peer than a concentrated attempt to overcome a singular opponent who has the advantage of swinging space and maneuverability. The Jedi work well side-by-side as though they've clearly practiced, but if their fighting styles differ, or don't stack well, they cannot hope to overcome an opponent through their efforts.
No matter how fast/precognition you have, you can't move block two sabers striking you at the exact (or almost exact) same time in different areas. If the duo could coordinate properly, then how do you block that?
But the entire point of defense is to make sure those openings never appear. When attacking a singular opponent, the idea is to box them in and wear them down, since they have to work twice as hard as their foes. However, a skilled defending swordsman knows the methods he's up against, and he works to make sure he's not in them.
Also, instead of wondering why the Jedi just don't stab quickly high and low and end it, the question should be "do the Jedi fighting styles really emphasize this kind of behavior"? Obi-Wan, in particular, is defensive-based, and his philosophy is about winning through superior defense. When he attacks, he's adapting his style to the polar opposite of what he's practiced for decades to master. While he can do it (And he certainly focused on it prior), it puts him in an uncomfortable position.
Anakin, for his part, is all about getting in the other person's face. When he fights side-by-side with Obi-Wan, he suffers from Obi-Wan's weaknesses as well. If the senior Jedi is unable to keep up the flurry, or his defensive-minded ways sacrifice offense for a mediocre defense, Anakin must pick up the slack. All while not slicing off Obi-Wan's limbs in the process, and not getting killed by a master swordsman who's style is strictly saber-to-saber and focuses on efficiency of motion just as much as style.