Due to the power of a relic, it is actually supposed to take a long time to get it. They did not originally intend for the Zenith to be so quickly achieved, but it happened.

You want a perfect example of why the relic should be originally harder to get, take a look at how many weapons exist at 50 that become useless once you get your relic. They were intended to fill that gap as you went through the steps for the relic, but the relic was so easily obtained they are now just rare drop skins in these dungeons.