I think the size of the Halla in game was ridiculous, considering that the Halla guy seemed to imply that they were the same Halla they used. However, I suppose a whole team of them could pull an aravel. May be the Halla in the past were bigger then, although that codex makes it pretty clear the Halla should be bigger. If they are wild Halla why are they only found in the Exalted Plains? Prior to the civil war that was farm land, so the farmers would have killed off the Halla pretty quick, particularly with the bounty for Halla antlers. Now you'd think the Emerald Graves would be an ideal place for the Halla but no, there we had August rams.
I always thought it pretty daft riding any sort of deer. Physically they are not designed for it. Plus the antlers get in the way. There is a reason why people tamed horses to ride and not deer. Reindeer are used as pack animals and to pull sleighs but not for riding.
I think that Dalish warriors would be charged with guarding the clan and protecting foragers when they go out collecting herbs and berries, etc. So they would concentrate on perfecting close combat skills, while the archers would predominantly engage in hunting. Since the race bonus is for ranged weapons, they sort of steered you towards making your Dalish a rogue or mage; otherwise your race bonus was wasted.
Slightly unrelated to Dalish but to do with slavery, I just realised today that Garahel, the great elven hero of the 4th Blight (a city elf) defeated Andoral, who was the god of slaves. Sort of poetic justice there I feel. I wonder if the writers did it deliberately or it was just coincidence?