So, the Gamer is pretty classless, and it has a One True Build in the form of the INT/Mage build.
This is because the only way to get more MP is to raise INT, and MP is needed for all skills, including those for ""warrior" skills.
Thus, a warrior must have twice the stat points to be as effective as a mage, since they must raise INT and STR.
In addition, Webcomic!Gamer magic, and those that copy it, is ridiculously powerful, versatile, and adaptable. A mage can make themselves stronger and faster with spells. And being good at one type of magic means that you can do any other sort of magic.
So, first, to fix the OTB problem, move MP, HP, and SP (if your system has that) to one stat - END/Endurance. This stat only affects the size and absolute regen of the pools. It becomes an important stat for any build, but cannot be the only stat in the build.
Next, fix the omni-mage problem by not having INT and WIS, but instead having schools of magic as the "stats" for magic. So if you put a bajillion points in "destruction" you won't be any better at healing people or locating magic traps or whatever. It gives the readers some sense of what the characters can do, and what they can pull out of their sleeves.
So, physical stat proposal, based on what I just said:
END/Endurance: Determines size of resource pools, and absolute regen rates.
STR/Strength: Determines power of physical attacks.
AGI/Agility: Determines movement speed and reflexes, but not thinking speed.
DEX/Dexterity: Determines control over movements, maybe also tied into senses?
As for school stats, I'm thinking about using the D&D schools as a starting point.
Abjuration: Spells that protect, block, or banish. An abjuration specialist is called an abjurer.
Conjuration: Spells that bring creatures or materials to the caster. A conjuration specialist is called a conjurer.
Divination: Spells that reveal information. A divination specialist is called a diviner. Unlike the other specialists, a diviner must give up only one other school.
Enchantment: Spells that imbue the recipient with some property or grant the caster power over another being. An enchantment specialist is called an enchanter.
Evocation: Spells that manipulate energy or create something from nothing. An evocation specialist is called an evoker.
Illusion: Spells that alter perception or create false images. An illusion specialist is called an illusionist.
Necromancy: Spells that manipulate, create, or destroy life or life force. A necromancy specialist is called a necromancer.
Transmutation: Spells that transform the recipient physically or change its properties in a more subtle way. A transmutation specialist is called a transmuter.