The interrupt rate for a blm is certainly op, it should perhaps still exist but with a much lower proc rate.
By sorting this out this would rectify the issue casters face (garuda/brd), there's nothing you can do to brd short of nerfing its dmg or adding gcd interrupt to its attacks. It should be left alone.
That being said scathe = DMG of a melee attack pretty much
A lot of the problems can be sorted by working together, brd sat there interrupting your healer? Mark 1 and all DPS burn them down