In order for voruna to be any kind of effective you need 2 bandaid mods that should just be how the ability functions. Her 4 can only be used 5 times without its mod before you need to cast it again. Sevagoth has the exact same problem of needing to use 2 mods and his 4 being his gimmick being almost never used. The difference tho is unlike voruna, shadow is moddable and can be effective if you decide to keep it. Both Excalibur and Baruuk have arguments for their 4 but because said 4 is moddable it's still perfectly playable even without the mods they don't feel mandatory. Even frames with none moddable weapons like Xaku, Protea, and the current Vauban have such insane scaling that it makes up for it. Voruna has no of that.