Elder-Basilisk said:Note that there's no point in asking whether sword and board is balanced with TWF. Sword and board is actually one of the best ways to utilize TWF. (It's a very feat intensive way to do TWF--and it just got more feat-intensive with the addition of two weapon defense which is better for sword and shield TWF than ordinary TWF because incremental increases in AC are more significant the higher the AC is to begin with). Consequently, any benefit to TWF is a benefit to sword and shield fighting.
The question should be "is sword and board viable without using TWF"? I think it's too early to see the answer to that. (Using a +5 shield takes the 3.5e pit fiend's chance to hit an AC maxed (+5 natural, +5 ring of protection, +5 mithral fullplate, 16 dex, +5 large shield dodge feat) fighter from about 60% to 25% or so (and, if the tower shield is really +4, +2 max dex it will either enable a fighter to achieve that AC with normal (non-mithral) fullplate or enable a fighter with mithral fullplate to do one better than that (or 2 points better if a mithral tower shield has a +4 max dex). That's clearly worthwhile but it's unclear if that is typical or whether monsters will typically have either a low enough AB or a high enough AB that the shield is largely irrelevant.
Now that we can agree on. Which is probably one of the reasons fighter's remain viable vs barbarians in 3e, since the feat chains are longer and their effects stack.