Savage Sortilege only applies to *magic* skills - so basically any spell that deal damage. As long as you're relying on weapons to inflict damage, you don't need Savage Sortilege. Shooting special arrows is just basic attack. And all weapon skills automatically use your crit chance just like your basic attacks.
Not sure I understand your second question, but elemental damage from weapon is tied to your basic attacks, so it is multiplied when you crit (either with basic attack or weapon skill) and it is not when you don't crit.
