Zevran's mother had a relationship with a woodcutter elf (city elf) and when he died, instead of returning to her clan, she became a prostitute in order to live. This would suggest that she knew her clan would not take her back.
Feynriel's mother had gone one step worse and had a relationship with a human. It may be that her true clan was back in Antiva and that she travelled to Kirkwall with her lover. Even so, she feels she is an outcast because of her choice.
Merrill sympathises with the city elves because she is now living among them. She has been cut off from her clan; although Marethari clearly hopes that she will see sense and return. It is part of Dalish culture that you are guided by the Keeper and elders of the clan. Merrill continually rejects their advice, again putting herself in role of outcast. So romancing Hawke is hardly the same for her as for a Dalish who is living in the clan and never rebelled.
The Warden had no choice but to leave the clan. At the beginning the farewell seems permanent. It was implied that joining the Grey Wardens meant leaving the clan for good and therefore I must admit that the change at the end where you can say you are going back did seem odd at the time. The Blight might be over but there are still darkspawn to fight; else why bother having people join the Grey Wardens between Blights? The lore has never been consistent on this. Originally the Grey Wardens is a lifelong commitment, then Alistair, Anders, Fiona and the Warden can up a leave if they want to. I feel really sorry for Jordy and his wife; the only guy who gets killed for not wanting to be a Warden.
Anyway, back to the Dalish. Whilst not all clans may be as extreme in their views as the Keeper in Masked Empire, they do look down on city elves and they are hostile, in thoughts if not in deeds, towards humans. I don't think they have enough contact with dwarves or qunari to form an opinion on them but it is likely it would be similar to their views on humans, without the history to back it up. A relationship with a dwarf or qunari would be condemned for the same reason as a human; any offspring would not be elves. Dalish are small enough in numbers as it is and there is great emphasis on the need to remember what it is to be an elf; I would imagine that reproducing with the correct sort of mate would be part of that.