*Proposition:
Decreasing the number of D6 of sneak attack on subsequent hit in the same round by 1. (minimum 1D6)
The Rogue is well balanced, but there is always room for amelioration. I propose some fine-tuning to prevent some possible abuses, without removing too much from the actual rule for sneak attacks. My proposition is not a big change in the mechanic, and is easy to implement.
With the new PFRPG sneak attacks rule, rogues get the chance to sneak attack more often. (new type of creatures)
When a Rogue is in a position to make more than one sneak attack in a round (Iterative attacks, Haste, Two-weapon fighting, Flurry of blows from multiclassing, Combat reflexes...), I propose to decrease the number of D6 on next hit by one. (minimum 1D6)
*Proposition example:
A hasted and flanking 9th-level Rogue (3 attacks in a round) will deal extra 5D6 on his first hit, 4D6 on the second hit, and 3D6 on the third (total 12D6 versus 15D6 actual rule). If there is not hit, there is no decrease. In this example, if the rogue hits only on his third attack, the extra sneak damage is the full 5D6.
As you can see, my proposition don't penalyze the Rogue very much. But, let's just take a look at this hypothetical situation (which may comes up only once in a lifetime) where it shows how crazy actual sneak attacking can get:
A VERY lucky 15th-level Rogue with greater invisibility and hasted, using Greater Two-Weapon fighting (Rapier and Shortsword), has 7 sneak attacks in a round. Assuming that all attacks hit (lucky rogue!) this is 7x 9D6 of damage.... 63D6! With my proposition, this number goes down to 35D6 "only". hehe...
Some players (not all!) often find ways to combine rules to put themselves in very advantageous situation, to the point of sometimes making the rules *seem* unbalanced. Flanking + Two-Weapon Fighting = lot of D6 of sneak!
Overall, I think that a Rogue (given his lower BAB), will not hit the target that often in a round, but I prefer something solid in the rule to prevent those rare and specific situations where things get out of hands...