Making your golem punches scaling with the size and sharpness of your axe is the worst possible way to make everyone needing loot. Here is some suggestions. Gear obviously should enhance your character and powerful characters should wear powerful gear because they are powerful, not be powerful because they wear powerful gear.
1 - Sacred runic system / D1 tome system
Simple. Mages needs to absorb the rune to increase skill level on sacred 1/2. And on D1, they need to read tomes and meet the required magical power to absorb the tome power.
1.2 - Adapted
Instead of always progressing linearly, why not tomes having different levels and learning fireball lv 8 not necessarily requiring to learn fireball lv 5?
2 - Rune magical system (actual runestones, not the loadout system of D3)
Diablo 3 rune is just a loadout system. The unique good thing that can be said about D3 system is that most runes are sidegrades, not upgrades. However, there are a lot of other games. Dungeon Lords and Gothic 1/2 are examples.
You can make runes with all levels drop from enemies or ingredients to make runes like G2 did. Necromancers on D2 has the bone spear. Necromancers on G2 ret has the spear of darkness. Both spells are the main skill which dark mages uses on both series, however, you just need to allocate the points to get the spell on D2. On G2 ret is different. First, the quest to become a necromancer is pretty hard, then you need to learn the third circle of magic(BTW, bone spear is a 3rh roll spell for necros on D2), then learn how to make the rune, get the ingredients and finally, make the rune.
Something like this
https://i.imgur.com/mQeBPRi.jpg
3 - mages needing to research their spells
Like project gorgon where to reach certain levels of certain types of magic, you need to research certain spells to evolve on necromancy or fire magic. Some high level spells require ultra expensive reagents like Phoenix Feather…
Not an power gain but - PoE inspired visual microtransactions for spells
Would be cool if you could have auras, transmogs like Trang Oul Set from D2 that transform the necro into a vampire. Having red, or dark purble bone spear would be amazing.
HOW GEAR SHOULD ENHANCE THE POWER
Remember, enhance the power, not determine the power. Gear should be a enhancement for your character capabilities, not the definition of your character.
Jay Wilson at 12 min on GDC criticizied “lots and lots of affixes in a item”, in favor of pure stat stickie gear. Video bellow.
And he mentions that having to worry about FHR, casting speed and other things hurts his “fantasy of a Barbarian”. Well, having to spend every single second looking for a bigger and sharper axe hurts an druid, monk, wizard, warlock, wathever fantasy too.
The main propouse of gear to a caster should be survivability. Enemies like Souls should be able to kill an naked caster extremely fast. And the enhancement to spells can be in faster casting speed, procs, +skill level, and other interesting things.
But please, no more 'your muscle mass and IQ is tied to the fanciness of your boots", magical gear enhancing your character capabilities is OK. Magical gear determining your character capabilities KILLS what is a character in the first place.