If u equip a VDW 1.4 Dagger in offhand instead of Gunship Axe u lose 0.05 sec on ur offhand swing, which will basicly make every 15th an extra off hand swing (Axe: 0.74 vs Dagger: 0.69 attack speed).
http://wotlk.openwow.com/talent#f0eb0tLZMtV0bcxqru0xRt
Goin this talent build, at BIS ofc, u could with eaz maintain 100% uptime on both Rupture and S&D.
With Mongose on offhand, beeing up almost all the time, with that 2% extra hit on dagger, u could soft cap the offhand swings (65% raid buffed + 3% from ret + 2% from talents + 2.xx% from Mongose).
@Fluffybully, could this be a viable item build? I know u lose Hack and Slash on offhand swings, but u basicly trade 5% rng for 100% extra hit with 2% more chance on crit... Thats atleast how i see it. Maybe im wrong? :D
Edit: Also, why do u feel the need to cap expertise? From how i see it, since u get the energy back, both feral and rogue dont need that expertise cap, 22 should be fine enough... I know ur white swings miss and u dont get them back but its like 1-2% of overall hits. Thanks.