drnuncheon said:
Parrying with both weapons is not "actively using both weapons"? That's a very strange definition.
It isn't strange at all. Unless you use the variant rule for parrying from the DMG, you never actively parry in the first place, thus you never actively use both weapons when it's not your turn, unless you've already used them in a full-attack action and your next turn hasn't come up yet.
The act of parrying is passive. If you have a shield and a sword, it is assumed you are using both to keep your defenses up, though this only really takes place in the background.
drnuncheon said:
The feat says "when fighting with two swords", not "when fighting with one sword and holding a sword in the other hand".
You make a very good point, but I don't think it can interpretted in just one way. I can understand someone interpreting it to mean "When you take the full attack action with two swords", but I interpret it to mean, "when you are armed with (or wielding, if you prefer) two weapons". Admittedly, we're now at the part of the discussion where I can only give you my interpretation of the rule, not a quote, since there isn't anything that solidly points one way or the other.
drnuncheon said:
The defending property is weritten differently - it does not say or imply that you need to take any action to get the benefit
Neither does Twin Sword Style.
drnuncheon said:
Two-Sword Style specifically says "while fighting with two weapons". Thus, to get the benefit of the Two-Sword Style feat, I think you need to be actively using the off-hand weapon.
So long as you acknowledge that this is just your interpretation, as I did, that's understandable. The feat does not explicitly call for any type of action to be taken in order to use it, no more so Dodge, which is also misleading if you scrutinize the description as much as Twin Sword Style.
Dodge states "During your action, you designate an opponent". Now, I could quite easily argue that Dodge requires you to take a standard action (or partial, or ME, or full) in order to use it, since it references action. Obviously, it is referring to your "turn", and not any specific action. Conversely, TSS style does not refer to any specific action either.
Logically, if you rule that TSS can only be used during a specific type of action, you must follow through with that ruling and apply the same restriction to Dodge. If not, your argument collapses and lack justification for your decision, barring rule-0 of course.
But, like I said, this is now just my opinion and my interpretation.
drnuncheon said:
The benefit of TSS over Expertise is that you also have the potential for one or more extra attacks.
And the drawback to TSS is that you must be from a particular region or culture in order to easily select it. Regional feats can be difficult to aquire, much more so than your average feat.