CapnZapp
Legend
A subclass that boosts damage under certain conditions is fair enuff.Subclaas to boost sneak attack dice is easy enough. 3 of the 4 assassin features boost sneak attack damage.
What I am talking about is extra sneak dice in general. Unconditional sneak dice, if that isn't already an oxymoron (they still follow all the rules for when sneak attack damage applies, I mean). A plain boost to the number of sneak attack dice. Walking around town with, say, 12d6 or 15d6 sneak attack dice (at level 20 of course) instead of 10d6. Always. Not just in special scenarios.
If the pinnacle of sneak attacking is 20d6 that's ten extra dice. Let's envision how these might be attained:
Adding a subclass should probably account for half those, easy. That's a +50% increase (a progression of +1d6 at low levels and +5d6 at very high level)
If we envision a feat, that's probably +2d6. But +2d6 is OP at low levels (and outright broken at very low levels), so this should probably either be a feat that firsts grants some benefit and then later on grants the remaining benefit... or simply a feat you can't take until, let's say, level 8.
Then the remaining three dice we can sprinkle out as other effects, say two items and one spell. If these give +1d6 each, there's no reason to make sure they can't be combined.
If a regular rogue takes the feat, that brings him up from 10d6 to 12d6 (assuming level 20). If a specialized rogue gets both items, that's 17d6 (again, at level 20).
