One aspect I liked most about skills in DA:O, was that I'd customize each Companion (and the Warden) to themes, specs, if you will, according to pathos and char development. For instance:
- Morrigan: "Dark"-like, hexes, sleep/horror, life-draining spells and whatnot - Entropy at large. Elemental spells (mostly Ice & Lightning - "weather") that made sense for a witch of the Wilds. And of course, Shapeshifting, which I maxed, gave her the Blood Magic spec really towards the end (not a big fan, but...), after she had acquired her mother's book and before the Dark Ritual.
- Wynne: Support. Healer extraordinaire. Crowd control. Glyphs, dispel magic, etc. Spirit (Spell Shield tree) and Creation, mostly, some Arcane. Only a couple offensive spells. Arcane Warrior.
My Warden was a heavy nuker, but overall well-rounded: mastered all elements except Earth, plus Telekinesis (CC), Ice and TK were her go-to, basically, spells she started with; she took a leaf of Morrigan's "wild, free-spirit" (as a sheltered child of the Circle) with Shapeshifting, and even the Robes, staff, etc I'd give her represented that sort of "freedom", more "bite "she had gotten. With Wynne, she got the Heals, buffs and that crowd-control aspect, remained faithful to the Circle and aware of her responsibilities of a Warden ; I'd say, even in terms of character my Warden came to really find herself as a sort of balance between these two polar opposites, in her mage companions, her friends, during their journey together. I thought that was nice. 
Same went for everyone else: Alistair - Sword & Shield only + Templar/Champion; Leliana with Archery (no dagger action!) while Zevran could cut a ...witch like no other Rogue, (though no Archery skills). Sten, sword. Oghren, hammer. And so on. No character was the same, which I loved.
In DA2 it was streamlined if just a bit but you could still do that:
- Hawke: Elemental (except Primal=Earth), Arcane, plus Force (which was awesome, love it). While Anders was all about Healing and support, basically; and Merril, Primal/Nature-themed spells, and her Blood Magic. As for my Warriors & Rogues, same thing I did in DA:O, basically.
Now, in DAI, while I'm *very* excited about all the new stuff (loving the Winter tree. And the visuals, OMG!), I do share some of the concern we'll be more limited this time around. Magic, in particular, I feel it shouldn't be. I do trust the devs, however, open to changes and hoping for the best!
As of right now, I'm (wasting my time, prolly
) thinking/planning, sorta kinda:
-Viv: She seems like the proverbial "Ice Queen" in every way, but definitely with a fiery side to her (don't touch her couture! lol) so I'm leaning towards Winter and Inferno primarily for her.
- Solas: I'm thinking heals. And I feel he's our guy in all things Fade and Spirit-y - so, that too.
- Dorian: Necromancer, I'm feeling Lightning and/or Spirit plus any and all more "dark"-themed spells, that vibe. Life/Death and all that, Heals and buffs might fit him nicely, as well.
- Inquisitor: TBD!!!
