Many people speculate that once 5.0 hits, getting your 4.0 relic will be nigh impossible due to the design of Eureka as a whole. The following is my recommendation on how to improve it.
TL : DR Light grinds always suck, here's a bunch of ways to alleviate it. Lessen RNG, increase light and crystal gain.
1) Decrease NM spawn timers / spawn conditions
Right now they sit at 3 hours. What this results in is people hopping from instance to instance trying after they've done a round of NM popping.
Also, mob kill requirements needed to spawn NM need lowered for later. Someone on reddit did a test and for Dino/Giz in Anemos, he had to kill **150** mobs before the NM would spawn. That's ridiculous.
Heck, People rarely see Cassie as it is currently.
2) Remove NM weather spawn conditions
Weather based spawn conditions in this game have never been implemented well do to weather patterns and RNG. Once the content dies down anything with a weather based spawn condition will be nigh impossible to complete. SE has sort of acknowledged this by offering Pazuzu / Louhi currency for Anemos / Pagos Crystals
3) Rebalance NM HP/Damage.
Many players seem to think that if an instance is dead, you could kill NM's by yourself if you spawn them.
As seen
https://www.reddit.com/r/ffxiv/comme..._people_skoll/
That's just simply not true.
4) For the light phase, anything over level 30/45 gives some form of light (even if it's feeble every mob).
Going through 60 enemies an not getting any light is frustrating. Or use chains as a sort of "Bad Luck Protection".
5) Change the challenge log to award crystals or light if you've reached the max level of the section.
This would encourage players to play the content they should be in. A popular tactic for the pagos section was to complete your challenge log in Anemos because Pagos was so badly designed. Putting Crystals or light in the Challenge log gives an alternative. Alternatives are good.
6) Put in daily quest NPCs / Levequest NPCs.
Why this was not done from day one of the Eureka content is baffling. This place is perfect for it. Use Grand Leves to spawn NM's that you can kill yourself. There NEEDS to be SOME sort of alternative than kill x mobs, spawn X moster.
7) Raise the ilvl sync
There is zero reason to have the level sync at 300 (other than artificial difficulty) when the gear rewarded is 355 / 380+. If you have to, make so that the gear rewarded from Eureka bypasses the ilvl sync. I also think this should have been in from the start. It would actually Encourage you to play the content for a reason other than relic.
8) Remove Death penalty when you've reached max level for a zone
Make it a reward for finishing the area. There's a reason games went away with exp penalties on death . . . THEY"RE NOT FUN. And remember, In SE's OWN words, "If it's not fun, you're doing it wrong".