Overview
DP-12's Mod gives her a lot of upgrades to her already decent pre-Mod form. She immediately gains an additional Armor, and another at 117, bringing her to 25 base Armor which is tied with LTLX. And then her SPEQ gives her an additional 1 Armor compared to normal Armor Plates as well as -1 Damage Taken. All combined, she is pretty much the tankiest SG before using any Skills.
Her Skills are still pretty much split into an active and a passive portion, with the Skill 2 just adding more effects to her passive. After Mod II, her reloads grant three additional effects: a 40% RoF self-buff for 8 seconds, 5 Armor stacking each time she reloads, as well as an additional HP Shield based on her Armor. Even after only one reload, these additional HP Shields are already a 50% increase in total HP Shields. The RoF self-buff makes her reload even more frequently and almost caps her by itself (SG RoF cap is 60), all in all a very good buff for her due to her scaling off reloads. The Armor has a max duration of 99 seconds, which means she caps out somewhere just above 20 stacks (+100 Armor), provided you leave her standing still and nothing gives her RoF penalties. As you can probably tell, this is absolutely absurd amounts of Armor.
Her Skill 1 remains mostly the same, except now also doing a knockback and slowing enemy Movement speed as well as having a much lower cooldown.
As DP-12 Mod wants to just keep shooting and reloading constantly, plus her SPEQ reducing her Mov even more, she should almost never be kited around and should just be left standing still to keep applying HP Shields and increasing her Armor. If what you are fighting requires kiting from the maintank, then DP-12 Mod is likely not the best option.
As she also needs to reload frequently, you should absolutely NOT put a Choke on her. You may use Birdshot if you so desire, as her SPEQ grants her the flat damage reduction that Flash is usually needed for. Birdshot grants her additional RoF (so you are now absolutely capped) as well as grants her additional chances to knock back enemies.