I looked it up, and it seems builds with Sky Opener always use Totems to generate stacks - which makes sense, the totem hits way faster than animals. 
For example here he used Storm Totem https://youtu.be/qFYqTH2d8CE?t=692. What’s noticeable is that when he actually uses tempest strike for a while, the stacks go down.
And here is a variant with 5 Thorn Totems https://www.youtube.com/watch?v=s5ECrZho9gs which can keep the stacks up.
I’m pretty sure that with just 2 Crows you would have to interrupt autoattacks and wait for them to generate stacks again.
If you roll a 90 lightning melee damage affix plus implicit, it still only gives you +76 spell damage. Exalted staff was +95. If the effects from Sword Catcher all count, it would be up to +152.