The problem is not your champions. The problem is your gear.
Stop looking at the champion power numbers. Those are not relevant. Focus on the gear itself. You want all of your champions to be using ONLY 5* gear or better - preferrably only 6* gear. And ONLY rare gear or better - preferrably only epic or legendary items.
But that's not enough to rest on. You also really need to pay attention to *what* the items are.
Top-Row Items:
The items on your top row - Weapon, Helm, and Shield - have fixed primary stats, so you don't need to worry about that part for those items. For those three, you need to make sure that the substats on the items are good. At your level of progression, I would focus on making sure all of your items have at least one "good" substat upgraded twice.
Substats:
Before I go onto the other items - what's a "good" substat, you ask? It really depends on your champion. Speed is almost always good. For your level of progression, Resist is almost always bad. FLAT Attack/HP/DEF are always bad - those are the versions that don't have the "%" symbol. If your champ is an ATK champ (like Ninja), HP/DEF are to be avoided. If it's a DEF champ (like Scyl), ATK is to be avoided. If it's an HP champ, like Miscreated Monster, ATK is to be avoided.
Bottom-Row Items:
This is the area most people mess up on. Bottom-row items - Gloves, Chest, Boots - can have a large number of primary stats, and it's critical you use the correct ones on the correct champs. You want Crit Rate Gloves on your damager champs, DEF% gloves on your tankier defense-based champs (like Scyl), and HP% gloves on your tankier HP-based champs (like Miscreated Monster). You want ATK% chest on your ATK champs (like Ninja), DEF% chest on your DEF champs (Scyl), and HP% chest on your HP champs (MM). For boots, you want speed on everyone.
Accessories:
These are much simpler. For rings, just use the same stat as your primary stat on the champ. Try to get substats that also match, but don't worry too much about it for now. For amulets, try to use Crit Damage amulets on your damagers, and for your other champs, just use whichever you find that's best. Banner is the one that is the most important - you want Accuracy banner on any champ that needs accuracy (Ninja, Scyl, Miscreated Monster, etc...). And you ideally want speed substat on that banner.
