Not sure if a thread has been dedicated to this topic, but I think it may be important to bring to the attention of some.
I have noticed alot of lower level characters...new and TR alike, running around swinging 2 weapons. I have also noticed alot of higher level characters with no TWF feats swinging 2 weapons. I think alot of people must have missed the change to how Two Weapon Fighting works with Update 5.
Here is a breakdown:
With no TWF feats you only swing 20% of the time with your offhand weapon
With only the TWF feat you only swing 40% of the time with your offhand weapon
With the ITWF feat you only swing 60% of the time with your offhand weapon
With the GTWF feat you swing 80% of the time with your offhand weapon
Tempest I adds 10% to offhand swings.
Tempest II adds another 10% to offhand swings.
Additionally, with no TWF feats, and no light weapon in your off hand, you suffer a minus 6 to hit with your main hand, and a minus 10 to hit with your off hand (on the 20% chance you are even swinging)
Lower level characters or those without at least ITWF should be using a 2 handed weapon or at least go S&B, as opposed to 2 weapons. Even using a 2 handed weapon you are not profficient in (-4 to hit) would be more desirable to a weapon your are profficient in (-6, -10).
Another factor favoring the use of a 2 handed weapon would be the additional damge you receive from a strength modifier.
Swinging a 2 handed weapon gives you 1.5 times your strength modifier added to damage. When using two weapons, your receive your strenth modifier on main hand, as well as .5 of your strength modifier in your off hand.
Additionally the advantage is also greater with 2 handed fighting where power attack is concerned. You get a 2:1 ratio of Extra Damage:To Hit Penalty.
There will be a point, depending on your build, you will gain more of an advantage from utilizing TWF. Before that point, pick up the 2 hander.
Another point to keep in mind, is that alot of popular builds that advocate using 2 weapons without the feats, were designed prior to U5, and not updated. There has been a few discussions involving a couple of these builds that do not take this into account.
Most of the people that read this will already be aware of these issues, and unfortunately most of the people that aren't aware will never read this. Hopefully at least one person will see this, and be able to gain some perspective on the issue.