I did some tests for bash & block with different jewelery with the following enchants:
Test A = Reduce stamina cost of abilities by XX
and
Test B = Reduce cost of bash by XX and reduce cost of blocking by XX
Note, tests are with the normal bash, not the skill. Tests were done with a 1H sword and a shield equipped. I created videos to study the results, but I'm not creating a YouTube account to upload them. My upload speed is horrible anyway.
First off, Test A also reduces the cost of bash & block, but for only half the amount indicated. It seems to me that if this includes bash & block, it should be for the full amount. Is this a bug? Or is this intentional, and if so, what is the rational behind it?
Test B jewelery is broken for block. It only reduces the cost by the same amount an equivalent level Test A jewelery piece does, and again being only half of that amount. (If it matters, I performed Test B tests with a ring, not a necklace.)
Test B for bash does the indicated amount, but cut in half again. (ie: An indicated cost reduction of 28 only reduces the cost of bash by 14.)
As it stands, "[Item name] of Shielding" with reduced cost for bash & block is pointless. With "[Item name] of Reduce Feat Cost" jewelery having reduced cost for all stamina abilities you will get the exact same savings, except for the little bit extra for bash, and it will ALSO reduce the cost of all your Weapon line skills!
Examples using Gold V3-5 glyphs: (Note, .5 values may round up or down depending on your total savings.)
Greater Glyph of Shielding (Reduce bash & block costs by 28)
14 = cost savings for bash
9.5 = cost savings for block
0 = cost savings for Weapon line skills
Greater Glyph of Reduce Feat (Reduce cost of stamina abilities by 19)
9.5 = cost savings for bash
9.5 = cost savings for block
19 = cost savings for Weapon line skills