Mana cost is still terrible

I'm playing CoC Invoker caster, and I have to spend at least 16 passive points and 1 annoint just for mana regen and mana cost efficiency to barely have enough mana for mapping

While attack-based builds can use the Viper unique helm and 1 support gem to fix all the mana cost, while having access to 10 other benefits of being surrounded??

You probably want a gear piece that grants decent amount of mana on kill. Also be careful about not levelling up all your spell gems all the way. For my Lich i leave Contagion for a few levels lower for instance which helps a lot. It doesn't put out enough dps on its own anyway and its main purpose is to get the combo with totems going. Maybe you have a similar synergy in your build that you can cut a corner with mana cost.