The Iron Banner Bounty to win a match with a score of over 2500 was doable when Iron Banner was control. It's -much- more difficult in Clash. You need at least 23-25 kills in a single match to do this and your team has to win.
In other words, unless you are simply mopping the floor with the enemy team, you are not going to complete this bounty any time soon. If you are going to use it for Iron Banner Clash, drop the score requirement to 1500-2000.
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I was able to complete the bounty on my first game, however, I agree it should be lowered to around 2000, which is still hard but a bit more attainable. I also think Bungie realized how difficult the bounty was which is why it hasn't been repeated.