Whoa, there, slow down on the upping the CR thing. Look at the numbers for the Attack bonus- vs. opponents worthy of level 10 characters, they aren't very good. Also, keep in mind what you'd be using for damage- if you're playing with the monk option (the most attacks available), then you are either using fists or a monk weapon. That's at most a d8 for damage. If you are playing any other class and using two weapons, your primary does, at most, 1d10, and that's if you blow a feat or play a dwarf. Your other weapon, optimally, does at most d8 (if using a double weapon), but more likely d6 or less. So, even if you do hit, you aren't dealing much damage.
Now, if you play a Tempest and use some feats out of Complete Adventurer, you could be wielding two 1d10 weapons at only a -1 to hit by 10th level. That's a little more dangerous. But then any good DM sees that a mile away and puts some kind of smack down on it.
BTW, forgot about Whirlwind Attack. You could attack up to eight opponents if surrounded, but then you'd only get one hit/target.