- At armor 17 or lower; the initial attacks inflict more damage on average.
- At armor 18; the average damage is equal, but only if every attack hits. The potential damage is also a bit higher for the initial attack option, and you don't risk loosing the entire damage pool on one bad roll.
- At armor 19 or above; the combo strike option pulls ahead in terms of raw potential damage.
- Target must be ARM 19 or better. [Otherwise the Initial attack option is better]
- Target must be at low health. [Health should equal 32, reduced by targets current armor score. Further modify the target number by current armor -23, for each available focus.]
- Target must be hit on 3+ in order for this equation to be anywhere near valid.
As you can see the combo strike option is really meant as a finisher, and only against Heavy Warjacks that are easily hit, and only if there are no debuffs available. There are rare heavy infantry models that require the same attention as a Khador Heavy, but generally it will be a poor trade to send in a Slayer against such a unit.