Check the mod priority guide:
https://docs.google.com/spreadsheets/d/1ty239kyJbBs1sLhTo1JvSWuN0mIJsK1nwVdI6OLLtXo/view?rm=minimalM1919A4 is an overall okay upgrade by itself, but comes with some decent utility if you can complete her SPEQ-Set.
So what does the MOD offer without the SPEQ-Set? Her Skill 2,
Devouring Terror, makes her always prioritise the closest unit and Crits now have a small chance to knockback non-elites and stun them for a short duration. She also deals 50% increased Damage to Giant enemies. On top of this, she gets the usual array of stat buffs and tile buffs, and her Skill 1 now grants additional Critical Damage.
Overall a fairly unimpressive upgrade, but if you can complete her SPEQ-Set, things get more interesting. Most notably, her Skill 1 activation will remove all HP Shields from any enemy Giants. This is pretty good, as HP Shields are plentiful and frequently found on Giant enemies (such as Hannibals and Patrollers). She also reduces all enemies’ Damage during Skill 1, though given the short 6 second duration, this doesn’t add much overall to the upgrade.
If you are capable of completing the
SPEQ-Set, M1919A4 MOD does offer something that could be worthwhile. Overall though, it’s simply an OK upgrade for an OK doll, and generally not worth too much consideration if you can’t complete the SPEQ-Set.