Know your skills.
As MRD/WAR if you keep Maim up you're keeping your enmity up by 20%.
Second Wind uses attack power so Berserk will help more than Convalescence.
1 enmity = 1 damage = 2HP restored. "Increased Enmity" is a multiplier. Not sure about GLA/PLD but for WAR it's
Skull Sunder = 3x Enmity Multiplier
Butcher's Block = 5x Enmity Multiplier
Overpower = 4x Enmity Multiplier
Tomahawk = 3x Enmity Multiplier
Defiance then multiplies the final total by 2.
Oh and as a MRD/WAR use flash (not Overpower) on sleeping mobs. Don't just forget about them.
EDIT: I forgot about Storms Eye - that 10% reduction in Slashing Resistance is actually really good as all of a MRDs skills are slashing which in turn increases enmity.