Sunic has it right in the first comment. You need magic to compete if you play by the CR system. If you nerfed all the monsters so you could kill them faster than they could kill you, yeah, non-magicians would be more viable. But magic-users would be so much better it wouldn't matter if you attempted to compare them.
Your party can do fine if you enable the other characters to fill their niches. Make sure they have things like Freedom of movement, and soem sort of teleportation to get out of the worst Battlefield control spells, and you should be able to take out most "Level Appropriate" encounters.
I don't really see how "hitting things with sticks" in 3.5 is that bad, there's plenty of builds and ways to go out there to make an awesome meele or any kind of glass cannon without casting even a cantrip :\
(...)
Just to make an example in a party I played two years ago or so the biggest damage dealer we got at levels 17 to 21 was a Barbarian (and he wasn't "glass-y" at all)
You still need either Tome of Battle (which is magic), or freedom of movement (which is a spell). For the most rudimentary of Battlefield control spells.
Even the best build Damage Dealer/supercharger Funky lunky I can kill everything in one round has huge troubles with things like Solid Fog, and even worse, Wall of stone. Unless they have some way of getting out of there. Which is usually a spell, and pretty much always magic.
So my advice pretty much is:
To make them viable, you need them to be able to avoid the things that makes them "un"-viable. Think about what you would do if facing their character? The usual response is something like Black Tentacles for the Rogue; Solid Fog, Entangle or Glitterdust for the barbarian; and Various other tricks for their various hybrids. You have to get them ways to get around this. This is the reason why most well rounded "beatsticks" use Tome of Battle. Iron Heart surge, shadow jumps and their speed altering friends help protect you against battlefield control spells. Which is pretty darn useful.
Also, consider having the Rogue/fighter retrain to something like this:
Feat Rogue 4/Sneak Attack Thug Fighter 3/Swashbuckler 3/Feat Rogue +10.
Get him Daring Outlaw, and he's sneak attacking much better. At the cost of a few BAB he'll also get neat rogue abilities, more feats, more skills, better saves and all that nice jazz. It is an odd reading of daring outlaw, but totally RAW. And not broken.
He would step on Beatstick ones toes though. But they really almost fill the same niche already. All three of them does actually.
Oh, and they all seem to be relying on precision damage, remember to get them at least true-death crystals. But properly also ways to sneak attack other things.
If the VoP monk can retrain, Monk 5/Ur-Priest 2/Sacred Fist 10 is decent with an Ur-Priest adaptation being about equal with a full caster around level 10-15. VoP Wont matter that much to a guy such as him. Although it is still bad.