Yeah, while it is cool that Riot does stuff to promote coming champion releases again, giving a mission to get 10 first bloods was not the best call.
Just 1 out of 10 players per game can get it, it can determine the mood of the other 9 people for the rest of the match. While I didn't get as far as starting to troll after missing my chance or trying to surrender, losing the first blood annoyed me for the rest of the match up to the point of tilting.
And it promoting inhealthy gameplay. To get this calling card, I spammed Warwick jungle and I did absolutely everything to take first blood away from my team.
Fortunately, over here in EUW it wasn't known by alot of people that such a mission exists, so there haven't been many people complaining about it.
But imagine if you are also trying to get first blood, you play an early game top laner for example, get your laner lol so you could possibly outplay and kill him in just a few seconds when your CDs are back up. But then your jungler swoops in, even flashes and does everything he can to take this first blood away from you, for which you worked so hard.
Learn from that, Riot. GIving us unique loot and missions to promote coming champions is great. But don't let us farm first bloods, it's causing too much frustration and leads people to work against their own team.