Wow 40 ranged defense is nuts! Is that with Dodge bonus? With Anticipation you should never get hit really (5% for enemy archers). Especially if you have some sort of cover.
It’s up to you though. If you already have Dodge and need the perk points somewhere else – with 40 ranged def Anticipation is probably not even needed.
As to how it works, GlyphGryph has it right I believe.