I'm spec'd BM, and up until Saturday night was wearing the S1 helm with a Relentless Earthstorm Diamond(+12agi, 3% crit) and +12 AP gem.
I ran Kara saturday and rolled on the Cowl of Defiance
I'm not hit capped, so I can use the +hit and extra AP.. but, my AGI dropped and my crit went to just under 20%.... I also using the Glyph of Ferocity on both
I'm wearing the Cowl of Defiance right now... did I make a good choice? I seems like my dps will go up, but I haven't played much since getting it to really see.