One trick pony that hits like a truck without any strategy involved no matter what enemy he's facing.
As for your list:
- Jean - CC. Heal. DMG is really not there if you want to use her as a main DD. Still, probably the most versatile standard hero.
- QiQi - heal. DMG also is not there.
- Mona - no DMG whatsoever, definitely not something you want to invest in. Taunt and Ultimate is what you are looking for.
- Electric cat - Good DMG. But can't kill shields and electro falls flat compared to Diluc's fire. Overall, a good starting DD if you don't have anything better. Elemental skill is ok, probably something without what she could have been a 4☆.
Diluc is just so much stronger than any above character that his one dimensional nature is not something that can bring his overall rating down imo. He's not a limited drop and can fit in any team no matter what. Don't compare him to Klee. She's in the league of her own. Just like Venti. Now that new 5☆ from 1.5 is definitely a scam.
Yeah, what about live fast & die young? She should have been a main DD with Hu Tao's kit. Living on the edge and doing insane DMG before her eventual premature death lol
You're really wasting your time and resources. Upgrade your main DD to 90 and raise your world level to the max. After that, farm to your heart content. There's no reason to level up everyone at the same time xD
My second favorite boss after electric cube. Very predictable, very easy to kill, no unnecessary additional phases. I kill him mostly standing in 1 place.