It's a level 8-10, so "weaker" to begin with doesn't matter, not to mention the complete opposite of how the game works. I have a character who does 1d4+2+4d6 damage at level 6, with a tiny knife that's not even magic.
I'm not entirely sure what you're trying to say here. Is it your contention that casters are actually weaker than other characters in 3.5? That flies in the face of conventional wisdom, but I'm willing to entertain arguments on the subject. A sneak attack that averages 18 damage isn't very convincing, though. A sorcerer at that level can throw fireballs for 6d6, averaging 21, and hit a group of enemies at the same time. Only so many times a day, of course, but it's not as situational as a sneak attack, either. Barbarosa's monk is much more compelling, but that's an extreme min/max build, and doesn't have that much impact on the game as actually played.
And really, direct damage is what casters are worst at. The real reason casters are better is that they can do so many other things. A well-played caster doesn't try to match a barbarian's damage output, he makes it a moot point by throwing negative levels and save-or-dies around, or with strategically-placed
solid fog spells to prevent melee altogether, or by confusing everyone with illusions and preventing combat from starting in the first place, or by dominating enemies and watching them tear each other apart, or...
Fighter-types are better at dealing hit point damage, but if you're doing hit point damage with a caster you're probably doing something wrong.
This is also a "story" campaign so while I will try to challenge you, I"m not trying to actively kill you like I would if I was running a low-fantasy dungeon delving campaign.
Fair enough.