You've never fought a 6th-level rogue, have you?
A 6th-level rogue with 9 ranks in Tumble and the Dodge, Mobility, and Spring Attack feats is an absolute nightmare for most parties. That's a free flanked attack against your primary fighter or anyone stuck at the edge of the party's defensive line at +3d6 damage per round. If we make it a human rogue with a +1 longsword, 14 Strength, Weapon Focus (longsword), you're looking at an attack at +10 that deals 1d8+3d6+4 damage (assume the rogue uses the longsword two-handed, since he lacks shield proficiency). Against a fighter in full-plate +1, a large shield +1, and a Dex 13, he hits 40% of the time and deals 19 points of damage per hit. If the fighter doesn't have a shield, he hits 55% of the time.
Of course, the rogue could just tumble past the warriors and hack the wizard to death. Mr. Wizard can toss a fireball at him, but if the rogue saves he takes a big fat 0 damage. If the rogue has an allied spellcaster who summons a monster to flank the wizard, the rogue now goes back to dealing 19 points a round, hitting about 75% of the time (assuming 14 Dex, +2 bracers, +1 ring of protection for the wizard). The rogue could also use Bluff to hide or deny the wizard his Dex bonus to AC.
For extra nastiness, give the rogue a level of ranger (Rog5/Rgr1) and have him take human as a favored enemy. It has no effect on his base attack progression and gives him a second attack at only -2 on both, a particularly useful feature against soft targets such as wizards and sorcerers.
If our rogue maxes out his Bluff and Hide skills, he can singlehandedly take down a wizard in the typical dungeon setting. Wizards do not get Sense Motive or Spot as class skills, making it very difficult for the wizard to spot the rogue or call his bluffs. The rogue can use his movement action to close to melee distance, then use his Spring Attack feat to attack and immediately move 30 ft. away back around a corner to hide again. If no cover is available he can stay in melee and wreck the wizard. If the rogue hides, the wizard's targeted spells are useless since he can't see his target and his area of effect ones more than likely deal 0 damage because of evasion. If the rogue initiated combat and wins initiative, he gains consecutive sneak attacks by using his partial action to move into melee and attack, staying put, and getting another sneak attack. He can then complete his attack action by moving his full move as per the Spring Attack feat then use his move action to move another 30 ft.
As far as rogues vs. spells, every class in the game is weaker than a given spell, but once a spell is cast its gone. At 5th-level my one fireball may deliver 20 points of damage to 8 orcs, more damage than a fighter can deal in one non-critical hit. Does that make a wizard better than a fighter? Of course not. After using his spell, the wizard is spent. The fighter keeps hacking. Same thing for a rogue.
A 6th-level rogue with 9 ranks in Tumble and the Dodge, Mobility, and Spring Attack feats is an absolute nightmare for most parties. That's a free flanked attack against your primary fighter or anyone stuck at the edge of the party's defensive line at +3d6 damage per round. If we make it a human rogue with a +1 longsword, 14 Strength, Weapon Focus (longsword), you're looking at an attack at +10 that deals 1d8+3d6+4 damage (assume the rogue uses the longsword two-handed, since he lacks shield proficiency). Against a fighter in full-plate +1, a large shield +1, and a Dex 13, he hits 40% of the time and deals 19 points of damage per hit. If the fighter doesn't have a shield, he hits 55% of the time.
Of course, the rogue could just tumble past the warriors and hack the wizard to death. Mr. Wizard can toss a fireball at him, but if the rogue saves he takes a big fat 0 damage. If the rogue has an allied spellcaster who summons a monster to flank the wizard, the rogue now goes back to dealing 19 points a round, hitting about 75% of the time (assuming 14 Dex, +2 bracers, +1 ring of protection for the wizard). The rogue could also use Bluff to hide or deny the wizard his Dex bonus to AC.
For extra nastiness, give the rogue a level of ranger (Rog5/Rgr1) and have him take human as a favored enemy. It has no effect on his base attack progression and gives him a second attack at only -2 on both, a particularly useful feature against soft targets such as wizards and sorcerers.
If our rogue maxes out his Bluff and Hide skills, he can singlehandedly take down a wizard in the typical dungeon setting. Wizards do not get Sense Motive or Spot as class skills, making it very difficult for the wizard to spot the rogue or call his bluffs. The rogue can use his movement action to close to melee distance, then use his Spring Attack feat to attack and immediately move 30 ft. away back around a corner to hide again. If no cover is available he can stay in melee and wreck the wizard. If the rogue hides, the wizard's targeted spells are useless since he can't see his target and his area of effect ones more than likely deal 0 damage because of evasion. If the rogue initiated combat and wins initiative, he gains consecutive sneak attacks by using his partial action to move into melee and attack, staying put, and getting another sneak attack. He can then complete his attack action by moving his full move as per the Spring Attack feat then use his move action to move another 30 ft.
As far as rogues vs. spells, every class in the game is weaker than a given spell, but once a spell is cast its gone. At 5th-level my one fireball may deliver 20 points of damage to 8 orcs, more damage than a fighter can deal in one non-critical hit. Does that make a wizard better than a fighter? Of course not. After using his spell, the wizard is spent. The fighter keeps hacking. Same thing for a rogue.