Yea there's not much play with the ele sham build imo but I'm open to be proven wrong. I just feel, like you said; -1 second cast speed needs to be taken.
I'd opt for something more like this:
https://classic.wowhead.com/talent-calc/shaman/55000115230215
The fire nova totem does respectable damage, but it costs so much mana. I guess you could argue it's life saving for quick burst melee range but I'd rather get the extra range on earthbind and reduce the cd of shocks by a further .4 seconds.
One could argue also that getting 15% increase damage on fire totems is a great way to go. Searing totem does pretty good poke if it's ignored. But again, I think that kiting with frost shock rank 1 and earthbind is the way to go, while conserving mana for quick offheals when needed.