But to answer your question a lot of newer teams are in the vein of "one zeta is OK, but 5 zetas are amazing" meaning they require all of them to reach full effective level. Sep droids are this way, Padme, and even Clones past one zeta.
The big ones off the top of my head are Bastila's lead zeta, where the added tenacity makes the team far harder to kill. Bossk's lead which gives the team a ton of regeneration. KRU lead gives them regeneration and extra tankiness. And Fives' sacrifice unique turns the Clones into a powerhouse in raids and on offense