Sometimes playing well involves bad kills / death ratios

I played a game (as Diana) that we comfortably one. I was surprised, therefore, to see my stats at the end show 3 kills, 9 deaths, 6 assists. It was a really weird game, however. Our team went 45/60 but only lost one tower on the way to destroying all of the other team's inhibitors and (as well as their nexus obviously). It was as lopsided a victory as I'd ever been in yet had that bizarre k/d ratio. But it got me thinking. There were two specific deaths in which I got a little overzealous at the end and probably shouldn't have attacked. Those two instances aside, all of my deaths were in skirmishes in which we killed people and/or towers. My CS was the best in the game with a wide margin between our 2nd person (only slightly behind me) and their best person. We killed Baron twice and Dragon once. The game went a relatively long time (37mins i think) largely because the other team was more fed than us (leveled faster but didn't have nearly as much gold as it turned out) and the last 15 minutes of the game were fought in their base almost exclusively.

So did I play well? I don't know. I completed dominated the middle lane (I was 3/1 by the time we started downing towers) and while I didn't get many kills, I was doing a ton of damage (most on our team) and generally making sure that their team stayed under 60% health and vulnerable to our other players. So I think I played well. But it was a game that emphasized to me the trickiness of making that determination.