You don't understand how their combat text works. If you damage something a few times very quickly, it will often merge those numbers and change one of the numbers you see instead of making a new one. When this happens, you didn't do that damage plus the other number you saw, you just did the total big number you see now.
This happens with Rifle Shot most of the time... You'll see your first shot hit for like 400 and then that number will change to 800. You didnt just do 1200 damage, you did 800.
Also I really don't even understand your Rifle Shot paragraph.
* Rifle Shot only hits 2 times, but you're saying you see 800 a couple times and that results in 2100 dmg?
* Even if you crit for 800 a tick with Rifle shot, that doesn't mean you "average" it to 2100. That would be assuming it crit 3 times I guess? It neither hits 3 times, nor crits every time.
Also, WoW does the thing where you get a lot more critical hits on lower level creatures but I have to see that confirmed in this game, and until we get actual combat logs and parsers, this is about as good as we're going to get.