One thing I liked about Alistair's romance was there were so many avenues to get on the romance track. It wasn't just structured events where if you skip a certain flirt line you miss out, so you reflexively hit every flirt instead of role play just in case. (I find myself doing that in SWTOR because you can't reload a saved game.) With Alistair, you can reply to his flirt with a flirt, you can initialize a flirt, or you can more subtly suggest your affection (by saying you care about him in certain dialogues). Most of his dialogues went at the player's pace. If all else failed, you had the "Has anyone ever told you how handsome you are?" which was an obvious romance starter. One helpful indicator of the romance being active was the affection bar, when it shifted from "warm" to "interested" for example. Another indicator was the different ways the companion responded when you talked to them, changing depending on how far you were progressed in the romance.
In contrast, with Fenris in DAII and the heart icon and the sequential talks, I don't know which is the flirt that puts you on the romance track, and which ones are just for fun. I don't know if it only takes one flirt to start the romance or if it is a particular flirt and I can't tell I'm in the romance until the one night stand event. I would rather play my toon as someone who isn't constantly spouting cheesy come-ons (because I'm worried about missing the romance window), but instead indicates affection when it's appropriate for her.
Agreed. You had a lot more options in DAO it seemed. Different approaches, and you could set the pace. The NPC can invite the PC to their tent once they reach a certain approval level, but the player can also take the initiative here and extend the invitation first. Or you can decline the NPC and wait for a later moment. I turned down Zev's massage for the first time recently ("not here, not now") and had my Warden invite him to his tent later. The whole approach and Zev's reaction was different, with him more teasing and playing coy for a while and some dialogue options ended the conversation without resulting in tent time. Asking again for him to join you led to him saying he seemed to recall hearing that invitation before and still would like to hear what they were supposed to do there. It was hilarious and felt very different from accepting Zev's initial offer.
In DA2 you indeed have nu clue which flirts are "essential" for the romance to lock in/remain active, and which are just (cheesy) pickup lines. In DAO one was enough and then you could continue picking and choosing which options you wanted and thought fitting for the situation. When I wanted to romance a character in DA2, I always chose the heart option, just to be save. This meant having to endure some obnoxious flirty remarks which would have felt more optional in DAO (I can choose to tell Alistair I dream of him and me having wild, steamy sex, but I don't have to as I know there are other ways to trigger his romance). The worst was Sebastian. My nice/diplomatic Hawke kept sounding like a perv who wanted nothing but sex and even offered herself up as a one-night stand eventually. Charming. That this relationship culminates in a chaste marriage is even more laughable.
The pace is also completely determined by the NPC in DA2. They show up at your house at some point "OKAY, I'M READY. TAKE OFF YOUR CLOTHES" and you have to take it or completely end the romance. There is no opportunity to say you are not ready yet, feel it's not the right time, etc. Just lie down and after that the NPC will go back to not talking to you (how many times I've clicked on Fenris...).