Ranged Mages vs Rogue Archers

I think a Dalish mage makes enough sense to justify playing as one 

Mages wear light armor and would not have any problems sneaking around if they actually wanted to. The problem is most don't seem to want to, haha. Using powers is noisy and obvious, but a dagger isn't. I believe quite a few of the mage outfits have a dagger equipped. So a mage has the capability of doing stealth kills should they need to. I imagine that all Dalish elves who are trained to fight are also taught the basics of stealth since they are so suspicious and cautious. So I don't think it's a big stretch to assume that a Dalish mage could be proficient at sneaking into enemy territory and spying. Also, one could assume since the conclave would have such a great impact on mages that the Keeper may have found it more relevant to send a mage.

Personally, I prefer playing as mages in DAI because I feel like it goes with the story so well. Plus powers are fun! :3 The only downside I find as a mage is not being able to move and cast spells. I have played as an Archer and it can be fun as well. Sometimes it can get a bit boring though. I definitely agree with the post above me that archers are better at dealing high single target damage and mages are better at crowd control. When it comes to archers vs mages I'm not convinced an archer would win against a mage simply because they could freeze the archer or use some other totally debilitating spell to incapacitate them. With that said, if an archer was to use an ambush style attack they would surely have the upperhand.

I played as a Rift Mage on Nightmare difficulty during my first playthrough because trophies, lol. I debated about being one of the OP and highly suggested specializations like KE or AW, but Rift Mage seemed like it would go with the story very well. I had tried KE but found it quite boring so I reloaded my save. It was really a lot of fun being a rift mage, I'm glad I picked it and recommend others try it. I only struggled a couple times and that is with hardly ever using the tactical camera because I hate it. 
So you don't need to be a Knight Enchanter or Arcane Warrior to be a very powerful mage on even the highest difficulty 

I figure that since a first of their clan is expected to eventually lead in place of their keeper, they'd have to train to be a leader and not an introvert sitting on their butt reading books. That'd mean twice the work helping, healing the clan, getting savvy enough about human affairs, when to avoid them and knowing how to bargain with merchants when it's safe. They do keep backups in a second and third so it's not too hard to see a mage accompanying hunters to increase the hunters' chances of survival. Since magic tends to manifest at puberty, the mages probably had the same training as the hunters until then. Dalish in Bull's Chargers proved that mages can crosstrain and disguise themselves.