TIER LIST FOR OFFENSIVE MAGIC
* Miracles - Lightning Stake, Dorhys' Gnawing
* Pyromancies - Great Chaos Fire Orb, Chaos Bed Vestiges
* Sorceries - Homing Crystal Soulmass, Farron Flashsword
* Miracles - Sunlight Spear, Wrath of the Gods, Lightning Storm
* Pyromancies - Great Combustion, Sacred Flame, Boulder Heave, Black Serpent
* Sorceries - Farron Hail, Homing Soulmass, Crystal Hail, Soul Spear, Crystal Soul Spear, Great Deep Soul
* Miracles - Great Lightning Spear, Gnaw
* Pyromancies - Fire Orb, Fire Whip, Firestorm, Chaos Storm, Black Flame
* Sorceries - Great Soul Arrow, Great Heavy Soul Arrow, Soul Greatsword, Deep Soul
* Miracles - Emit Force, Lightning Spear, Divine Pillars of Light
* Pyromancies - Fireball, Profaned Flame, Black Fire Orb
* Sorceries - Heavy Soul Arrow, Great Farron Dart, Dark Edge
* Miracles - Dead Again, Lifehunt Scythe
* Pyromancies - Bursting Fireball, Fire Surge
* Sorceries - Farron Dart, White Dragon Breath, Soul Stream, Pestilent Mercury, Affinity
Source: I've got about 150 hours of PvE and PvP time on each character dedicated solely to casting. If anyone needs a guide on how to play a spellcaster in duel scenarios let me know.