HeapThaumaturgist said:
I just don't see the ground for the argument that it doesn't stack.
Clearly, by the rules as written without any errata, it stacks. There is no real RAW argument that it shouldn't stack. But there are these factors:
1. Wizards makes many errors in their books. Some are fixed with errata, some not.
2. The introductory flavor text for the feat does not match the results of the feat.
3. The table text for the feat does not match the abilities of the feat.
4. The +2/+2 is suspiciously like the +1/+2 you already get from Weapon Focus and Weapon Specialization: the feats mentioned in the table and prerequisites for the feat. If the feat had given out +1/+1, there would be far less room for argument.
5. A stacking +2/+2 for Weapon Mastery is way more powerful than Greater Weapon Focus.
5a. GWF requires F8, WM requires F4.
5b. GWF gives +1/+0, WM gives +2/+2.
5c. GWF works with one weapon, WM works with all of the same damage type.
So the argument can be made that the "intent" of the feat is to not stack. Perhaps the line was left off, or perhaps it was deleted. Or perhaps that was never the intent. But there is certainly an argument to be made for that being the intent.
My questions are for those that say it was created to help out fighters because fighters are so weak. Where has this been stated? Where is this intent found? I cannot find it in the feat because it only helps out F4s. Finding F4s in a campaign isn't that tough.
And does Wizards really think fighters are weak? Where have they said exactly that?