Check the mod priority guide:
https://docs.google.com/spreadsheets/d/1ty239kyJbBs1sLhTo1JvSWuN0mIJsK1nwVdI6OLLtXo/view?rm=minimalST AR-15 has been through some ups and downs with the meta. She was once upon a time the pinnacle of ARs when it came to DPS, then her usability fell off for quite some time, but she is now back in the spotlight once more!
ST AR-15’s Skill 2,
Crime and Punishment, has her pull out a secondary weapon that deals 10% of her normal damage (bumped up to 20% if she is attacking an opponent marked by Seal of the Avenger). This gives ST AR-15 good sustained DPS in long fights against unarmoured or lightly armoured enemies. Since she fires two shots at once as well, she mitigates the issue of leaving enemy dummy links with a tiny amount of health left, which is somewhat helpful for her DPS capabilities.
ST AR-15’s newfound success in recent times though is found in her SPEQ-Set! Not only is it always accessible for everyone (all parts of the SPEQ-Set are permanently available in game), it also helps to offset a large portion of her shortcomings. With the SPEQ-Set, her second weapon now comes with surehit and ignores all Armor. She also gets a 6% Damage increase every time a unit leaves the battlefield (including summoned entities, such as T64’s clones) up to 10 times for a considerable 79% Damage boost at max. This brings her up to the same DPS level as G11 overall, but without the FCC cost.
If you choose to upgrade ST AR-15, it is definitely advised to go for the
SPEQ-Set overall. MOD2 and MOD3 alone don’t do enough in today’s meta to truly shine, but with all parts of the SPEQ-Set permanently available anyway, there’s no excuse not to get it! For newer commanders, it is recommended to upgrade her to MOD1 for a quick and cheap performance boost, then upgrade her further when you’re ready to complete the SPEQ-Set.