If Turbine is going to make Twilight not work for warforged, then Arcane Sigil should be restored to former stacking status. Either warforged body feats count as armor or they do not and we all no they do and should in every way.
The purpose of the docent is to easily deal with enchanting the warforged body. It is a cheesy work around but not because it's broken. It saves the devs headaches. Lets not use that as the excuse to hand down a nerf that essentially says wf armor can have spell failure reduction.
Some of you that are going to respond will argue that that isn't what is being done. You will be wrong. Arcane sigil and casting dex do not stack with one another. Arcane sigil was and is(unless they allow twilight to docents) twilight for docents. Casting dex and twilight do stack. Simple right?
Let's just give Turbine the benefit of the doubt and assume this was an oversight on their part and not more warforged arcane hate. I'm sure they didn't mean to reduce our options and enjoyment, right? Btw, as it stands currently a Mithril Plate(wf don't have a mithril plate body, many would choose it) wearing, mithril tower shield using fleshie caster has lower ASF without having access to enhancements than a wf does with after what they did.
Twilight was already superior to Arcane sigil just on the virtue of it having a higher max value. Why take away casting dexterity from wf as well? (I fully expect wf hating trolls that wish this was the Realms to respond in force...as usual to any wf post)