I notice there have been a lot of posts saying that Grandmaster (5 profs) has been nerfed (and there are "patches" to fix this). This is not true. It has merely been changed and balanced. The attacks per round depends not only on the characters level and profs, but on the weapon's speed factor. By reducing the speed factor, you are increasing attack rate. This may not be quite as good as the "extra attack" but you will see they modified several speed related profs and specialization levels that also use this. This balances the leveling more and makes it a bit more realistic.

To test this theory, you can take two kensais and bump them to level 18 and give one full dual-wield on long swords and the other full two-handed swords and two-handed wield. You would think that the overall damage from the dual-wield character would be better overall since with mass strength bonuses (I used two half-orcs) the double whammy with more attacks from the dual wield would produce more damage. I wondered why anyone would ever NOT dual-wield.

Then I investigated the weapon speed factors. With full specialization in two-handed wield, it decreases your speed factor in the weapon enough to give you almost the same amount of attacks per round (4 vs. 9/4). The two-handed swords do slightly more damage which makes up for the 1 missing attack every 4 rounds, thus making the two almost identical. In 1v1 battles, the two kensais were about even with regular weapons, and so the real factor became the power of the weapon. Well, for this two dualing Kensais are a bad example, since many of the weapons are geared towards combat with monsters, and 18th level Kensais make almost every save with the weapons I tested, so it didn't matter much. Against monsters it would, however, giving an edge to the dual IMO since you can have the Crom and "something" else.

I also wanted to note that that weapon you hold may seem powerful, but you may do more damage with a "lesser" weapon overall due to the speed factor. The Vorpal weapon is a prime example - sure it has a good chance (25%) of taking out an opponent, but only if they FAIL the saving throw. At the point in the game you get this weapon, most of your opponants will make most saves verses death. The Soul Reaver with it's speed factor of 6 and special abilities that do not have saving throws will kill more baddies than the speed factor 10 vorpal blade.

This testing also confirmed the importance of being able to have profs over 2, increasing my theories that Rangers and Paladins are inferior to pure fighters in most hand to hand combat situations.

Hmm, not sure how the speed factor works. It'd be get more studies on this. For example, when my blade wields the celestial fury and gets 3 attacks per round (in offensive spin), he seems to be attacking much faster than 3 attacks per round. But perhaps the graphics of him attacking are misleading, and we have to have the "misses" turned on. The celestial fury has a speed of 2. But slings, for example, have very low speed factors and they do not appear to attack more times than crossbows, with extremely high speed factors.

We also don't know how much speed factor goes down at proficiency 4. What happens when a weapon has a modified speed factor of less than 1? Is the extra speed wasted, or does it still have an effect?

How much does speed factor go down when you get four proficiencies in a weapon? Is it two or is it one? If it's two, then dual wielding katanas will give you two extra attacks because katanas have speed factors of 2, I believe.

A speed factor of 0 gives you an extra attack per round. You will see that on the short sword of quickness and some daggers you find in the game. They use speed factor on the weapons a LOT in BG2.

GW the graphic will include misses and swings as well, don't count the number of swings as that can be misleading.