If we look at the other two class that are designed around using their weapons (warrior and ranger) they have spells that can helps with auto attacking, such as mark buffing auto attacks or warcry buffying your attack speed. However, the base Rogue only have 2 spells that are purely focused on damage.
My suggestion is to either give flurry of blade iframes, give debuffs to enemies by default, or make flurry of blades destroy projectiles just like how on hoh1 thief can destroy projectiles by attacking.