Regarding my thoughts on the OP's suggestions:
1 - Yes, provided warriors get their own DW skill tree. Ability trees should be class specfic to allow them to be properly integrated into that classes design and playstyle, instead of having bland abilities than work for multiple classes. A DW warrior should be completely different from a DW rogue, somethhing DA:O failed at.
2 - Yes on more specialisation options, no on being able to chose multiple of them (and in case anyone else suggests it, no to being able to change your specialisation in a repec). By limiting the player to one specialisation with no chance of changing it, the developers have made your choices on the matter far more meaningful. They've made the spec far more part of your character than before, and that is a good thing, even if it reduces the total amount of choice available.
3 - No. Vitaar are a Qunari thing. Lore wise, they can only be used by Qunari. And the lore should be adhered to. That's what make world immersive and interesting.
4 - Yes. That's not to say I wouldn't want some DLCs, but a full scale expansion would be very welcome. The former are great for adding extra content into the existing story, but the latter are so much better for continuing the plot.