I only have one of the two RPers playing right now, but he is playing a wizard who focuses on enchantments.
I'll assume that when you say he's focused on enchantments, you mean to imply that he actually specializes in it, so that he gets the bonus spells and other advantages. I personally hate the enchantment school, as almost everything has a save, and when the enemy saves, they usually suffer NO effect (as opposed to half damage). Also, under the magic rules it notes that if a person makes a saving throw, they are
aware that hostile magic was cast upon them. This just makes the whole deal sucky, IMHO.
It's also one of the only schools of magic that gets overlooked in splatbooks. For example, there are NO 5th or 6th level enchantment spells in the Spell Compendium. Complete Mage, which came out after Spell Compendium and which you might
hope has lots of options actually
also ignores enchantment for many levels. If anything would help, your wizard really needs Mass Whelm from Player's Handbook 2 (10d6 nonlethal to 14 enemies), Freezing Glance from Frostburn (paralysis ray you can shoot as many times as you have levels), and Hiss of Sleep from Spell Compendium (powerful sleep, no HD limit).
Anyway, with such a PC, I would be throwing at him more puzzles, riddles, debates, dialogues, negotiations, and so on. Sure, he isn't going to shine in combat, but he picked the talky role playing spellcaster, so to me it's slightly a matter of "you made your bed, now lie in it."
Having said that, I believe there are ways to use his skills in battle. For example, if there is a mid-combat surrender, his character may be the right one to put together a peace settlement. It's still talky, but it IS going to happen in the middle of a fight.
Fear effects will get the enemies running, compulsion effects will get hostages to talk.
Or consider magical traps that, yes, can be disabled by the rogue (with real high rolls) but
also can be short-circuited by a wizard that is armed with Dispel Magic. For example, I just used the magic missile trap in Dungeonscape (called an "encounter trap" because it requires
all members of the party to help disable them). I had 4 small pyramids, one in each corner of a room. The door shuts & locks after they enter, so they're trapped. The tips of the pyramids begin to spin as if charging up, and then they unleash magic missiles. The fighter runs up to one and knocks the top off. The rogue runs up to one and uses Disable Device. But the wizard casts Dispel Magic and the other two shut down.
I know they are both playing whisper gnomes; which as I understand are a broken base race.
Their weight limit is 3/4 of normal, and all their weapons are small size (and so do less damage). At the level of play you're running, these notes are probably irrelevant, as they have ways to compensate (bags of holding, huge sneak attack bonuses, etcetera). But it's worth looking over the character sheets once to be sure it's all by the book.
He took the class in order to have access to all knowledges and the domain power that let's him take a move action as a swift action a certain number of times per day.
I would note that Fharlanghn offers
no domain power that allows for a move action as a swift action. His domains are Balance, Celerity, Luck, Portal, Protection, Travel, Weather. And
that's only if you allow lots of splatbooks. None of those domains offer such movement. It would make sense that the Celerity domain would offer access to the Lesser Celerity spell, which
does grant movement as a swift action, but unfortunately that's not what the Celerity domain offers.
So I would start to scrutinize these min/maxers a little bit more.
A Rogue wielding a Spiked Chain is also not overpowered. Spiked Chains are one of the few exotic weapons that are worth the cost a feat, and should logically do better than a more common weapon.
Agreed. Feats are very rare and grant abilities that you shouldn't undermine. If they decided to spend one of their few feats on it, then that's an ability from which they should gain some benefit.
Both of these characters generally cry when the undead, constructs, plants, elementals, oozes, or anything that is immune to critical hits and sneak attack comes along because their precision damage is suddenly worthless.
I had written a reply that noted that many of these types of enemies will also be immune to the wizard's focus on mind-affecting spells. However, I can see that you edited your post to add mention of that already. So instead, let me note a few interesting monsters that will allow the wizard to shine while the rogue & scout have to work twice as hard to make an impact.
1. Elementals are immune to crits & flanking, but apparently are subject to mind-affecting spells.
2. Abrupt Jaunt wizards can use an immediate action to teleport away from an attack. Normal wizards & sorcerers can use Lesser Celerity to emulate that class feature. This would create enemies that can spoil a devastating weapon strike, but that would be vulnerable to mental charms. The naga sorcerer in the free module "Treasure of the Black Veils" was pretty fun, and could be easily modified to have celerity spells. Spells such as Stay The Hand, Sonic Shield, Invisibility, G'Elsewhere Chant, and Mirror Image will frustrate melee attackers, while leaving a spellcaster with area effects fully capable.
3. Get out of melee range, simple as that. These min/maxers can't do a whole lot to stop 10 archers standing 65' behind the tank, whereas the wizard has many ranged spells. Nor can they effectively deal with a fighter that uses a bow and the Ranged Disarm feat to cripple their attacks from a distance, while leaving the wizard capable. Though to be fair, it might be possible to use Ranged Disarm on the wizard's spell component pouch, at which point the wizard will be limited to spells with no components.
4. Consider enemies that are stupid but powerful. Why? Because the wizard can put them into a state of paralysis with a single low-level enchantment spell (Ray of Stupidity, Spell Compendium). Put them up against a Purple Worm (or many!) and watch as they either slog through dealing 200 HP of damage, or else allow the wizard to cast Ray of Stupidity once, rendering the worm unconscious. Why? Because the purple worm has a Intelligence of 1, the ray does at least 1 point of int damage, reducing intelligence to zero. Zero intelligence = catatonic. Other monsters roughly appropriate for your campaign: Dire Elephant, Twelve-headed Hydra, Tyrannosaurus, and Quetzalcoatlus (bonus: they fly, so let's see spiked chain hit
that).
Good luck. Have fun!