Mana leech for crossbow skills that convert 80% phys to elemental? - how??

Hey all,

I'm fairly certain I don't understand the mechanic change for poe2 but I'm here asking to be sure.

TLDR: So my question is, how are you all solving your mana issues and am I missing something huge when it comes to mana leech?

Most crossbows and bow skills convert phys to elemental damage and yet there are mana leech nodes in the tree areas with little mana regen. But when you're only leeching on 20% of your non-scaling damage, that doesn't seem very helpful.

Currently I'm running a 5 link voltaic grenade with some other stuff but I basically get 2-3 salvos out before I need to chug a flask. I have over 100% mana regen, with clarity, mana font on totem, and another 30% on the tree with the rest coming from gear. It's not nearly enough. I need nearly double that, and that seems ludicrous.

Sure, mana on kill is fine for mapping but boss sustain is where I really feel it. I've resorted to the mana leech support on my basic attack and have tried to scale that a bit but I don't really feel much difference with just the 5% from the gem.

Thank you so much for your help!