Some of them are just paced for the pvp crowd that are in it for the long haul.

Plus, achievements that cater to people who don't care much for playing PVP itself seem to me to be of questionable value to the PVP community. The short term events like currently with Rival Wings being incentivized are fine because they draw in a lot of people who end up sticking around and playing ~regularly. If all they did was briefly ruin match quality it wouldn't be worth it.