Certainly isn't common. Only examples I can think off the top of my head are Aveline expressing serious doubts and Isabela expressing serious apathy.
Well true when it don't have to be common i doubt that peoples disbelif in gods can't exist... that always was in case and aveline was more agnostic than atheist when isabela doesn't say much on that topic...
Warden could express disbelif in maker even human could say that just superstitions hawke was enforced to be andriastian but well to be honest rp in da 2 was terrible and i m worried because of 3 possible responses in dai it will end still same when my character will be enfored to care or follow religion more or less like hawke it is bad when mass effect crushes you in creating you own character when you can be atheist or religious there...
I guess what there saying is that the belief of believing in absolutely nothing doesn't exist but you don't have to believe in the Maker. It would be odd to be an Atheist IMO in the Dragon Age world since there is magic.
How don't beliving in god can't exist do you mean that you can't not belive in god?Magic hardly matters in beliving in god as morrigan said fact that magic exist doesn't mean that maker/or god exist same with nature if we have nautre and other world not does that mean there is god? Well i think that you mistaken with someone that doesn't belive in anything atheist can belive in for example philosophies , humans ,science or other set of belifs even buddhists are atheists.