For Slime: First set of adds, have shadow flare up already, case bane/miasma II, then use spur>rouse>enkindle with garuda and they are dead in seconds. For 2nd set use limit break after people stack, 1 shot them all.

For King: I just dps boss, leaving shadow flare up, pop a bio on occasional tonberries to pull them in and add a miasma II as necessary.