The only thing that pops to mind regarding Karma's current design is "bland"

Seriously, she's bland as fk. Her kit has barely any inherent synergy, you don't really have any "balancing offense vs defense" going on, she's straightforward and boring. Typical skillshot with some AoE and a slow, yay, targeted tether that's worse than LeBlanc's E in every way apart from having 0 counterplay for melee champions to deal with it, a shield, and an ultimate that empowers one of these abilities. If the basic skills aren't interesting, or they don't have interesting empowered effects, well the ultimate is gonna feel bad obviously (and so will the whole champ).

Also finally please figure out a direction on her. In midlane she is a waveclear bot with no real playmaking, in toplane she shuts down melees stupidly hard without effort, in botlane as supports she's barely even played these days. It would be great to see her become a proper support or mage, rather than some failed combination of the two.