Does Mass Slaughter Need Sprucing Up?

Loyal, imaginary readers may recall that the Slayer class in Dying Sun have an ability called Mass Slaughter, which is just my renaming of the traditional Fighter benefit of multiple attacks against low-level opponents. As it stands now, the text reads like this:

Mass Slaughter – Slayers gain additional attacks when fighting rabble i.e. 1 Hit Die creatures. They receive a total number of attacks equal to their level. Thus a 4th level Slayer gets 4 attacks versus rabble (instead of the regular 2), while a 10th level Slayer gets 10 attacks (instead of the regular 3). These attacks cannot be split between 1 Hit Die creatures and those of greater Hit Dice; all Mass Slaughter attacks must be made on 1 Hit Die opponents.

There have been debates about this ability for as long as I can recall, specifically as to whether or not it is any good.  I like it and think it fits in with the presumed "end game" of YAG, but it does somewhat depend upon the kind of game being played.  If you are playing game where higher level characters can expect to be  involved in mass battles against armies which are largely composed of 1 HD soldiers, then this ability rocks.  It allows the high-level PC to scythe through enemies like a Greek demi-god.  On the other hand, if your high-level play continues to revolve around dungeon-crawls then I think we would have to say that the ability isn't too useful.  In a high-level dungeon-crawl, you are basically fighting high-level monsters (this situation is somewhat akin to the high-level Cleric and his Turning abilities which JB recently discussed).

Now, I just had a sort of idea that might be interesting.  It wouldn't entirely alleviate the dungeon-crawler's lament, but it would add a bit more versatility to the stunt.  The idea is that Mass Slaughters applies to creature's of Hit Dice not exceeding 1/3 (round up)of the Slayer's level.  Thus, it works for 1 HD foes from levels 1-3, adds in 2 HD foes from levels 4-6, and 3 HD foes from levels 7-10 (which is as high as my charts go).

In a traditional setting (i.e. not Dying Sun), that would mean that 4th level Fighters would get extra attacks versus foes such as Hobgoblins, Gnolls, and Zombies.  Under the Dying Sun, that would give the guy extra attacks versus foes such as Sand Ghuls, Troglodytes, and the weird hawk-hounds known as Darzai.

Why 1/3 of the level?  Well, it means that you get a boost at 4th level, which is the point at which the Fighter traditionally becomes a Hero and at which you have moved from Basic to Expert level play (or Low to Mid level, if you prefer).  Of course, the next transition is traditionally 8th for Fighter (Super-Hero) or 9th (Name level).  But since my scope of levels is lower than usual, I'm comfortable with 7th.  If you wanted to push further than my chart into 11thg level, you would then transition to 4 HD beings.

I think it might add a little lustre, as it were, without being too powerful.  Other thoughts?