Issue occurs on all characters I have tested. The card is an overall nerf to speed until you offset the debuff with another passive move speed card. Your speed is still nerfed regardless of what move speed cards you have as long as you have Burst Fire but you'll feel the effect less.
In Testing as Viper, my base sprint speed is 9.0 m/s. While shooting it decreases to 6.7 m/s.
When I have Burst Fire, after shooting a player and gain the +1.5 m/s move speed, my speed is reduced from 9 m/s to 8.5 m/s. While shooting, my speed is reduced from 6.7 m/s to 6.4 m/s. Burst Fire seems...