In my experience the Spitfire is best as a secondary weapon. As tempting as it is to use like a spooled-up Devotion, it just doesn't have that "run in and wipe everyone" power.
However that massive mag size lets you keep on pressuring when more bursty teammates need to reload, or that wraith is making a run for it, or if you want to pop a few low-risk shots at someone without worry about leaving yourself with a shallow mag.
Its niche is consistently being able to bring damage, rather than being a frontline ambush weapon.
Just my 2c, keep it comin'.