Full analysis
AAT-52 is an entirely uncompelling MG, and the first reason for this is her statline. Her 79 Damage and 24 Accuracy do nothing to bolster her effectiveness, and her standard magazine of 10 is her only redeeming stat. Due to her low Accuracy, AAT-52 actually tends to do less damage in her first volley than M249 SAW, who has 2 less rounds in her magazine than AAT-52 does. Considering SAW is generally not seen as a good MG to use, this does not bode well for AAT-52’s effectiveness.
AAT-52’s Skill may initially just barely seem to make up for her stats, but it too holds her back as well. Providing an 85% Damage increase in Night missions and a 30% increase in Damage at daytime with an 8 second Initial Cooldown, this skill just barely allows AAT-52 to outperform every 2 Star MG besides LWMMG at Night, assuming the battle goes longer than 20 seconds. Unfortunately, since most SGMG Echelons seek to end the battle within the MGs’ first volley, this invalidates AAT-52’s Skill almost entirely. Even if this Skill were to come into effect and she was able to fire her whole volley, AAT-52 would lose in total damage dealt to practically every single 3 Star, 4 Star, and 5 Star MG, as well as LWMMG who shares her rarity.
AAT-52’s tile buff is also fairly terrible, granting a 20% increase to RoF to a single SG. This isn’t particularly useful due to SGs having an already very low RoF, making a 20% increase to their fire speed not actually noticeable. Furthermore, because of the calculation behind Rate of Fire increases to Reload Speed, this tile buff often just changes an SG’s 11 second reload to a 10 second reload. Even if one wants to argue this is actually significant, it is important to remember that SG’s primary role is to tank, meaning that their damage output is almost completely insignificant.
Overall, AAT-52 just has too much going against her and not enough going for her to be good. Her terrible damage output, Skill that won’t see use 90% of the time, and tile buff that is essentially meaningless means that her negative qualities vastly outweigh and outnumber her strengths. If one is desperate for a 2 Star MG to use, they should use LWMMG instead and avoid AAT-52 on sight.