Glasgow hit back with a second score from Evans, who burst a massive hole in the Bath line, although James did reduce the deficit with apenalty at the end of the half.
To compound Scarlets misery, hooker Rees was sin-binned for a dangerous tackle on replacement Tani Fuga, Malone landing the penalty to reduce the gap to three points.
After the break, Mitu missed with apenalty effort but made amends soon after by slotting the ball between the posts to reduce his side's deficit to four points.