Hmmm, this is actually a little tough. Is the Cleric using Divine Metamagic (Persist)? What makes it tough is that just straight class wise those guys are actually pretty tough. The Paladin and the Fighter are pretty weak, usually, (though with clever optimization they can be much improved). But, Cleric, Druid, Bard, and Wizard are all solid, 3 of them are the toughest base classes in the game.
That being said, these classes can vary wildly in power. Straight Wizard who memorizes nothing but Fireballs and Straight Wizard who religiously follows Treantmonk's God Guide are very very different types of things at the table.
On top of that, your DM seems to have a long list of problematic misconceptions. Let's take your Fire Sorc example. He did 160 points of damage over 5 rounds. That's just over 30 damage per round. For a 10th level character that's actually ... crap. On top of that, the DM has jacked up the monsters in a way that says "fuck you melee," so the weaker builds (e.g., the Paladin and the Fighter and presumably your Rogue) get smashed whereas the inherently stronger concepts can mostly ignore it.
I'm also just guessing here, but I imagine there's going to be a bit of an anti-optimization vibe, as well. If that's the case, I'd say no to Spellwarp Sniper. I actually like the PrC, but it's most clever tricks are the sorts of things that a DM that seems to hate both attack rolls and charopp will hate even more.
For the record, I think a well-built Rogue should work fine in such a situation. Although that's a melee character, so it takes some charopp to pull off given your DM's seeming hatred for it. But, I think it's perfectly achievable. If I were so inclined to do that I'd go for a hit and fade Swift Hunter type, which fills the same Ranger/Rogue idea you were originally going for. The way I'd build that character is actually probably a bit exotic, and so not suited for your gaming group, but a ranged Swift Hunter seems like a pretty good idea since you are high enough level to qualify for Greater Manyshot (right?). Otherwise, use the Travel Devotion or any other idea contained in the Handbook.
A more flexible, and so maybe easier to contribute idea is the Unseen Seer, which is a pretty straight Rogue/Wizard hybrid. Throw some debuffing spells, do the occasional sneak attack aided by the Bard's buffs (or that hits Touch AC anyway), Cloud of Knives and stuff like that ends up being an actually pretty decent spell for you, and call it a day. Unseen Seer gets you access to Hunter's Eye, which I wouldn't even bother persisting (assuming I'm reading the tenor of your gaming group right). Just use it for a pseudo-gish buff when needed. For example, you can throw that plus Trollshape and some flanking and really tear into somebody if the mood strikes you. Other than that, Scorching Ray, etc. supported by a little bit of sneak attack and some decent feat selections and you should be good. I'm not 100% sure how you reliably pull off sneak attacks with spells -- somebody more plugged in can tell you that. Off hand a wand of Swift Invisibility is handy. There's a similar way to do it with feats and dips into Warlock, but that may be inefficient. Or, maybe even just hide in plain sight would pull if off if your checks are good enough.
But, the sneak attack thing isn't even a necessity to make the build work. Just pick some solid spells (see the handbooks here) and you'd be a nice skill monkey/wizard hybrid.
Hope that helps. I think either of those options should work fine, again, provided I'm following what your table looks like.
