I can see pros and cons of showing an iconic protagonist. An advantage of Hawke is that someone can have that outfit on, with the blood smear, and people will recognize "Oh that's Hawke." It's not that the details of the face necessarily even need to be precise. Put on that armor with the smear, and people will recognize it. It's a type of branding that could be important.
Even if it crosses gender/sex, I think someone like Holly Conrad (or a plethora of other women!) can dress up in the N7 armor and people will go "Yeah that's Commander Shepard." She certainly doesn't look like man Shepard, or even that much like default woman Shepard. In that sense, I think marketing did something right, even if the iconic character had a particular look.
For something like Dragon Age: Inquisition, maybe it'd be better to have that iconic look be a bit more generalized (since it's more than just human), but I'm not sure that the mere existence of an "iconic look" is bad if it can result in people identifying a particular outfit as being "the armor of Dragon Age Inquisition's main character." I'm not sure how much a box art specifically needs to explain what the game content is really like, or rather more catch an eye. In this case, as the women in this thread have pointed out, by having a woman on the boxart (or in marketing in general) could be useful in catching the eye of someone who values that. From there, they have picked up the box/clicked on the link/whatever, and from there supplementary content (in the article, on the back, etc.) can explain what the game is. Some may go "oooo" and some may go "naaah" but that initial hook, to me, is pretty important for a lot of potential customers.
I do think that there is a risk of a cover being potentially TOO busy (I'm a big fan of the Dragon Age covers because I find them very clean, and eye catching -- which may be a personal bias), as well as too sparse. I think it's also important to have a degree of consistency in the style, so that different marketing attempts don't conflict with each other in terms of making an association in a person's mind.
In this sense (note: I'm not a marketer, and I'm just thinking on the fly), for any individual piece of material, whether it be a box art, poster, or even trailer, I'd probably go with a randomized selection of a race gender, but all wearing the same armor set. With this, you could still show off physical differences between races/sex with each promo piece, while maintaining an aesthetic consistency between all of them so that the association of "that's the Inquisitor" can be reinforced. Then for the box art, any reference to the protagonist would be made simply to the armor (possibly with no one inside it -- literally just have the armor placed somewhere) used in other materials, with any actually fleshed out characters being party members. And I'd probably still keep the Blood Dragon since I think that that is a pretty iconic look for the franchise itself.
Anyways, my musings before I head off to volleyball.