It is simple. You need tons of energy (and time) to get to the top.

I don't know why this epic needs almost the same amount of effort compare to legendary fragment summon

Probably one of the requirements in december fusion event? 

For me the big question with dungeon divers is always, to what extent do I focus on dungeons and to what extent do I just keep running campaign (yes, campaign artifacts count too - of course campaign drops are mostly common/uncommon items and shards, so less points from those, but on the other hand campaign costs less energy per run). 

Often, like also now, there will also be an actual dungeon tournament running at the same time, Dragon in this case. Anything I gain in dragon will give me points in both the dungeon divers and the dragon tournament - so ok, that means I definitely want to run a lot of dragon, at least until I get the desired rewards from the dragon tournament. But when there is a champion training going on together with the dungeon divers, it means campaign is more interesting to run. If all three are running together, it's a tough choice and sometimes I really have to calculate closely how many more runs I'll need for a certain reward in one of the three. 

Another factor is whether I have an active XP boost - when I have one, of course I want to run campaign and level champs as much as possible before it runs out, so I'll postpone the dungeon runs, if possible. 

But anyway, if you want to get the high level rewards, it's extremely difficult if you can't run the higher stages in dungeons - and even if you can, it takes a lot of effort. What's the highest stage you can reliably farm in Dragon? 

One thing I sometimes do is going on a gear farming spree when a Dungeon Divers and a dungeon events/tournaments happen at once, and I could actually use some gear from said dungeon at the moment.

The current fragment Epic is of no serious interest for me, so I shall just happily not pay attention to it.😴