Minstrels have a moors relic that gives -10% inc healing on song of soothing i think it is.
Burgs get a relic that does gives -10% on subtle stab.
As I said previously, hunters get the bonus on merciful shot with 4 pieces of the predator set (I don't know the %)
Nyrion mentioned the -30% on essence of winter already.
Routing Cry 4-set bonus on the Loyalty moors set gives -35% for cappies
Onslaught, Warden's Triumph, and Adroit manouvre give -25% for wardens in melee stances only that stacks to -50%
I don't know how potential stacking on the non-warden ones work.
P.S. why Boar's rush over combination strike for burst damage? even with the slightly higher crit change, boar's rush on a crit hits softer than a regular combination strike.