Yeah, I think it's really important to remember that by the time they finally hook up, it's been YEARS of flirting and spending time together. It seems rushed to us, but there's a lot that we can assume happened without us holding the controller.
My headcanon with Anders was that my renegade mage volunteered in the clinic with him. She was his right-hand gal and they had a great, healthy relationship. But I don't need hours of playing them flirting about kittens and snowflakes, I only needed to see the ugly bits where Anders revealed how insecure he was...how scared he was of hurting her, because even before he met her in the estate, he was madly in love with her.
I think the problem lies in the fact that we HAVE to headcanon so much, because his storyline was unfulfilled. But I think context clues are ok to go off of. You know they're close. You know how he feels about her. It's alright to assume that we only see those ugly bits.
(Also, I told myself that she invited him to live with her after that. Because seriously, sleeping in the clinic was dangerous.)
My Hawke's gender was different, but the pre-romance relationship was similar. They were close friends and allies before they hooked up. I headcanon that he made a few passes at Anders which were rejected, leading to an uncomfortable period where they became closer, but the pain of rejection was still there. After losing Carver to the Wardens in the Deep Roads, Hawke really wanted something he could hang onto. That Hawke is not emotionally strong or independent, but he has been forced to let go so many times, he felt as if he would never stop hurting. Fenris kind of happened and it was disastrous, and then Isabela, and nobody wanted to be with him. He took it personally. But Anders was still there, and he genuinely seemed to need and appreciate Hawke.
Mostly, I take issue with the need people seem to have of not being able to praise one character or ship without tearing down another. I am uncomfortable with the assertion that one ship is "better" because it implies that the other ships are wrong, somehow. They aren't. All have their advantages, and all have their disadvantages. The ones you prefer are those that resonate with you. I like the Anders romance because I like the slow-moving, emotional trainwreck. I like the Isabela romance for emotionally stronger Hawkes because I like how they can be independent and uncommitted, but still very much in love. I like the Merrill romance for the reasons Galagraphia stated. Fenris is a hard sell for me for personal reasons, but I can see why some people like him.
The thing to remember is that this is the Cullen thread, not the Anders thread, or the Fenris thread, or anybody else. People are here because they like Cullen. They like a lot of other things besides, and sometimes, they like unpopular things, but they aren't wrong for liking those things. We get enough grief on the BSN as it is without finding reasons to divide us.