master strike is actually a pretty minimal increase for focus due to the fact that focus almost never runs out of rage and master strike doesn't reduce the cd on sweep, zealous leap. so, each time you master strike, you effectively increase the cd of the next sweep by 2 seconds, which offsets some the gain you would get from using it instead of slash. example, my vicious slash does around 2600 including force lash, my ravage does around 6800. so you gain 1600 damage from doing ravage. However my smash does 8.3k fully buffed. Since the cd is 8-9 sec Increasing the cd by 2, decreases by dps of smash in that time by around 20%, or in this case around 1600. The numbers aren't exact, but close enough to show that ravage is a very minimal increase in dps for rage spec and is more used in the rare case you are out of rage and battering assault and berserk are on cd.
Pulling numbers from a handy Focus parse
- Master Strike averages 2107.32 per tick. It ticks 6 times with 3 ticks at 77% accuracy (but this is accounted for in the averages). Thus, the average damage of one activation is 12643.92
- Slash averages 1578.09 per tick. It ticks twice with one tick at 77% accuracy (accounted for in the averages). Force Lash is 192.59 per activation. Thus, the average damage of one activation is 3348.77, or 6697.54 for two
- Force Sweep averages 7346.48, with a per-second use rate of 0.096666667, or once every 10.34 seconds. Subbing out Master Strike decreases the CD by 2 seconds every 30 (ignoring costs), which drops the per-second use rate by 0.006710311.
Thus, subbing in double Slash instead of Master Strike sacrifices (12643.92 - 6697.54) / 30 = 198.21 DPS to gain 7346.48 * 0.006710311 = 49.30 DPS. Verdict: LOSS
The only way this would be a benefit is if you're consistently hitting four or more targets with your Force Sweep and you're able to otherwise fudge your rotation to absorb the added focus costs. I can't think of any bosses where this applies over enough time to matter (Dash'roode only has two Xuvvas per pack), and so I think we can call this a general loss.