You are all making an interesting point about the gap but I think you are exaggerating it a little bit. The problem is, we just had the dragon event and those bosses were harder than this weeks boss or the bosses before the dragons.

That said, until the past two weeks, all I had was the big four maxed. I didn't have any of the 3* story armors. Despite that, I was able to get notus+ and phyrus+ using only my big four. (I couldn't get boreas+ or eurus+ because my big four weren't even maxed at that point!) To do this, I had to spend 22 gems to summon notus two times because I couldn't beat the level 42 boss. For phyrus, I used 20 gems on E early on so that I would have more time later to use my friends.

I also know people who got all the boss+ armors using the storyline armors. (The bigger four). If you find that storyline armors aren't getting you to level 43 on the boss, you either have weak friends, or don't know how to effectively maximize your energy usage. Now that bosses have dropped back down to Deva stats, the big four should actually be more than enough to beat the bosses to level 43, assuming you have at least 10 level 100+ friends with legendary armors. Many people probably would disagree with me, but I am speaking from experience. I DID unlock 2 legendary+ armors using only the big four. So it is possible, the gap is not too large yet. And it is definitely not too large for people with Swamp, Roc, Infernal, and DP. It should be effortless if you have those four maxed.