I found playing without offensive spells challenging in a really fun way, and man my Hawke was tough; by the end of Act 3 she had more constitution then Fenris. 
I understand missing the specialization; I love to play healers because I'm fascinated by healing as part of a character concept. I guess for me saying "DAI is a new game" is enough for me not to pine for it. I'm really excited to see how their new system works. There's a lot to discover, and I feel like a lot of fears will be mitigated once we're in the gaming environment and it all comes together.
The new design also seems like it may nudge me to play a different kind of character, which is something I like.
Interesting, I had a different experience. One of my Mage Hawke's was totally support oriented. Only spec'ed into Spirit Healer, Creation, Spirit, Arcane, and Force Mage. Always had healing aura active. Only offense (somewhat) move I ever used was mind blast. I found it to be an almost BROKEN playthrough. Literally invincible.
Sustained Abilities always active: Healing Aura, Heroic Aura, Arcane Shield, Arcane Weapons.
Active Abilities: Heal, Group Heal, Revive, Haste, Mind Blast, Dispel, Glyph of Paralysis, Glyph of Repulsion, Gravitic Ring (<--most important)
I kind of miss this playthrough lol by the end of Act 2 I was a God.
But early in the game it was pretty challenging, considering I almost always played on Nightmare. Once I was about level 14, it was all over.