So, in my second playthrough as an elf rogue (First was a dwarf tank), when I got to the choice between the templars and the mages, it was a COMPLETELY different line of events. Not even similar in the way it played out. Different layout, different story, different things happening. It even changed the timing in the introduction of one of your companion NPCs. I was stunned.
Now I just got back to Haven after recruiting this side of things, so I'm not sure if there are any differences once I close the rift, but I was absolutely floored. I've already seen differences in events based on my world history from DAK. And some side missions are different due to the character itself (Elf v. Dwarf).