First things first: NO MORE NEW CATALYSTS. If I have to fortify fifty different kinds of casting mediums to cast fifty different broken spells, I will snap dark souls 2 in half (the disk, and the computer it's on).
Second: I have this sort of pipe dream where each of the three and ONLY THREE magic styles have so much variety that they fill out all the possible roles in their own archetypal way. I feel like each magic type manipulates a kind of energy, with Miracles manipulating kinetic and electrical energy, Sorcery controlling chromatic and electromagnetic energy( this being souls), and Pyromancy controlling thermal and chemical energy. It is through this that I think the magic types are to be sorted.
Third: I will now sort the ideas I have seen into each magic.
Miracles: Support, Support, and more support. Lots of offense, but the offense doesn't deal nearly as much damage and instead offers plenty o' support. Necromancy and Lightning will be the main offensive roles this style embodies.
Sorcery (Soul-sell-y): The ultra mega super hybrid, with a bunch of mini-families of spells that do different things (damage, SUPPORT, aoe, stealth). Souls, crystals , darkness, fire? (Izalith), and light. Lots of light.
Pyromancy: This is gonna be a doozy
I like the idea that this is the stat-less magic, the poor man's way of fighting back the arrogant nobles and corrupt priesthood. But it needs to cost more and be MORE POWERFUL. I view this as the scientific-y magic, messing around with your molecules to turn you into an iron bulwark, so I think ice and wind magic should be some of the sub-types.
Ice needs to be less like the fairy ice magic from other games and more like hard science type stuff (no glitter, just cold). So more instantaneous effects because cold is the absence of heat and cannot be hurled into a magical sphere and thrown. An aoe sub-zero spell that slows everyone down and reduces the potency of fire comes to mind.
Wind is probably going to be abused, so it either has to be slow or cast-intensive. Bad lag? Lets make your opponent suffer for abusing your poverty by knocking him around with a wind storm (At this point I hope they add collision damage into the game). Also, most wind magic will deal a mixture of physical and magical damage.
FOUR: Pure magic must become a viable alternative. It was in Demon's, it was too weak to be in Dark. Thanks to the great Arcanatia for this scenario
Anyways, in order to balance melee specialists, magic specialists and hybrids;
1: Have viable weapons require higher parameters to be effective so that melee classes will need high parameters to deal good damage to to survive significant damage, weakening hybrids
2: Increase the effectiveness of armor, making characters with heavy armor more playable
3: Add a parameter requirement for armor. For example, a melee character will be required to have a certain strength or other parameter to use a heavy piece of armor with high poise, meaning a hybrid can only use weak/light armor.
4: Add a wider variety of spells, especially ones that don't directly deal damage, including summoning, controlling enemies, illusion, self-buffs, others-buffs, others-debuffs, traps, temporary weapons and/or armor, and fast, short-range spells
5: Require higher parameters for spells or have them deal lower damage at the minimum parameters requirements. This will, again, weaken hybrids, thus making dedicated mages more valuable
6: Have characters be able to still move while blocking. (at least if they have a high enough stability relative to the attack or spell) This will help make it more reasonable for a melee character to catch a caster and/or archer
7: Increase arrow damage
8: Enable archers to still move (perhaps slowly) while shooting, though not while aiming zoomed in
9: Add a nonmagical weapon upgrade path that can rival with magical or buffed weapons. This will enable true non-magic builds and add some variety from elemental and buffed weapons.
Finally, FIVE: The Souls series needs a cross-hair and a well oriented third-person camera so that we can aim our magic ourselves instead of relying on a lock on and homing. Needing a lock-on all the time gives birth to spells like Pursuers, and we all know how that turned out.