“Why are Dragon Emperors so bad?”
Dragon Emperors is generally considered to be one of the worst default uber banners for a few reasons.
Most of the emperors are outclassed by Ururun for general usage.
Most emperors have poor niches and ability sets, typically carrying knockback + slow which tend to get overshadowed by non uber procs.
Most emperors are either very below average or horrendously awful in mobility, making their flexibility terrible and their niches or any possible redeeming factors even harder to use and justify.
“Why is Dioramos so high? Isn’t he a generic backliner?”
Bulk, bulk, HP, bulk. This is the thing that differentiates Dioramos so much compared to any other backliner. He is one of the tankiest backliners in the game which is perfect in an end game environment where there are many backliner and piercing enemies which are set in place to disrupt stack meta, or at least stacking with fragile backliners. Dioramos defies this with his humongous HP stat combined with huge offense which lets him tank through and laser nearly every single stage in the game. Other details such as his attack pattern/ cycle being perfectly timed for maximum DPS contribute majorly to his overpowering strength compared to other backliners like Anubis or Amaterasu, who barely stand a chance with their DPS downtime and zero capacity to bulk.
"Why is Babel somewhat high? I thought he was an awful tank?"
Babel's tanking against Red and Floating means any stage that contains these threats are dealt with easily by his millions of HP, allowing you to focus on every other threat on the stage. It also helps that he has a ton of immunities which makes his kit significantly more optimized than most tanks. His kit is ideal in all but mobility.