Tempest/Earthquake/Blizzard/Inferno are pretty much the same spell - AoE nuke. Shock/Cone of Cold/Flameblast are the same spell - cone AoE. Stonefist/Winter's Grasp/Lightning/Fireball are the same spell - single target damage.
Different elemental damages are an important system. It allows your mage to spec in a certain element, which will get them advantages in some encounters and disadvantages in others. Not to mention, the elemental damages usually cause other side affects, such a burning, freezing, shock, etc, which is suited to different playstyles. These choices allow you to further define a character (i.e. of course Morrigan would be an ice queen) and also balance your party's abilities.
Mana Drain/Mana Clash/Mana Cleanse - same effect.
What, no they aren't. Mana drain absorbs mana from a single target without costing you any yourself. Mana cleanse costs the caster mana and simply nullifies the mana of enemies in an area without gaining you any. Mana clash on the other hand costs mroe mana but damages enemies along with nullifying their mana.
Not only are those all different effects, but they each have different mana costs and cast times associated with them. That isn't bloat. Those are options.
3/4 hexes do basically the same thing (increase damage taken)
That isn't true
Hexes are:
Lower resistances of single target
Lower resistances of enemies in an area
Lower hit chance of single target
Raise critical hit chance on a single target
Those are the same at all, and simplyfing it as "increase damage taken" is disingenuous.
spells designed like Paralysis/Mass Paralysis or Weakness/Miasma or Rejuvenation/Mass Rejuvenation are found throughout the game where the same spell is essentially available twice - which actually plays out OK (AoE vs single target is a legitimate decision assuming the mana cost differential is meaningful - I don't recall) in the game but also serves to really artificially inflate the number of "options" it looks like you have.
It provides a 'legitimate decision" but still "artificially inflates the number of options"? No, that not how it works. It is a legitimate decision, and is therefore a legitimate option.
I don't think that actually makes a big difference to the final product - people using, what, maybe 5-10 spells?
That isn't how Dragon Age played out, and it sounds incredibly boring as far as character development goes.