Overview
Stechkin becomes an even greater RoF buffer with her Mod.
She gets most of her bonuses at Mod I, increasing her tilebuffs and Skill effects.
As her Skill 2 is mostly irrelevant (due to pretty much only buffing her own damage output), there is little reason to worry much about it nor Skill Level it.
Her SPEQ-Set focuses primarily on RFHG team capabilities, with up to 3 instances of teamwide taunt towards the highest Damage enemies and also additional damage that can crit for RFs during Skill 1. This is decent, but ultimately optional. Mod III is not recommended unless you can complete this SPEQ-Set.