If you really did get a 34-3 in countdown im sure you played your damn ass off. But the 34 number may not be actual kills, and partially assists as well.
I saw a video this streamer posted saying he got 27 kills in one game, i watched it and counted 18 kills with 9 assists adding up to 27. Still a good game and something to be proud of, but its also inflated and misrepresented by him.
I'm honestly not too worried about kd anyways. I know that I win 90% of my gunfights and outplay the majority of players in the beta. Never got serious about Destiny 1 only ever had 1 weekend where I actually tried to get flawless and got it with a pick up group. This destiny,however, is a lot more gunskill oriented and frankly, more fun because of it. This is all just my opinion but I like the current state of the game. And as far as KD goes I'll just consider like a 2.5 a good kd regardless. Unless they have a stat of "average damage per game" then I'll say like 2,500 or higher is considered a good player.