Hello and good day to you sir. I saw your mod a few days back and decided to have a try at it. It is fun, and me and my cousin are having a good time using it. Thank you very much for this. That being said, I would like to report a possible bug and chime in a few suggestions.
First of all, a minor bug report. After importing all of the codes into the game, it will split into 3 categories. 2 Insta-Health category (the first sit between the Medical Kit and the Ammo category, and the latter after the Ammo but before the Grenade Mod category) and an Ammo Category (Tediore's Supplies). I also importing an insta-health vial to determine which group of Insta-Health it belong; The 2nd category.
Now, at the time of my writing, I can't produce this exact bug. The nature of the bug is, if you trying to sell a few of grenade mods or/and shields, sometimes, rather than proceeding to the next item below when selling your unused grenade mods or/and shields at a vending machine, it will skip upwards and as a result you can accidentally sold one of New Vials' mod. Only a minor inconvenience, but it make user be wary of selling their unused loot absentmindedly.
Also I noticed, when you use or in the process of selling loots, it will trade place between the 2 Insta-Health category. Not that it is unique in this case as the weapon's list also move about as you selling your loot. I don't know if the bugs are triggered by the existence of the 1st category as I don't have a strong evidence to support that, nor do I possessed an UDK or the knowledge of utilising it. Needless to say, I believe, this bug can be avoided by grouping it all into the 2nd Insta-Health category, as it was already existed in the game itself.
I also would like to raise a few pointers on several of your vials attributes, and a suggestion for your consideration;
Whilst having a higher accuracy and recoil reduction is good on their own, it also came with a few caveat. Higher accuracy is extremely important on a weapons that emphasise on a well place shot, and best to utilise it at far and beyond range; i.e. Revolver Pistol and Pump Action/Semi-auto Sniper Rifle. On weapons that mostly used for a short and medium range, and also on a automatic weapons, a high accuracy will decrease the size of the reticle. Against a large form of enemies, this feature become an absolutely hindrance during a frantic dodge-and-weave, and this is made much worse when using a shotgun. On the other hands, a recoil reduction is a much welcomed boost for an automatic weapons, as it allows the user to control the burst from firing haphazardly all over the place.
Therefore, I would say, it is more beneficial to separate the Increase Accuracy attribute into its own vial. The other attributes of Dahlminator needn't to change.
An increase in rate of fire is a blessing and a curse for a shotgun. Most of Assault/Combat Shotgun have a decent rate of fire if not good (for a shotgun), a high degree of power per blast, but suffer a high recoil and a low magazine size (which this vial has already rectify the problems). If rate of fire is the priority here, then a Double Anarchy's SMG will fit this much better with their much more controlled burst and sustained fire than any shotgun could hope ever do. Also, there are matter of preference and novelty.
Thus, if I may suggest, kindly remove the Increase Magazine attribute, and transfer it into the Infinum vial. The original Infinum attributes can be made into a new vial, manufactured by the Eridian. I believe this would much fit in the lore.
Maybe you could incorporate a passive health regeneration as an addition to this vial. After reaching level 5 and onwards, and after investing some points into Action Skill and Skill, all the playable characters could regenerate health passively without Tediore's shield, or engaging in a combat. Except Mordecai. His healing skills need him to leeching it off from an enemies (without Tediore's shield) or reduced to scavenging for health vial/kit in a pile (single player only). Also Roland's action skill's cooldown are long. Perhaps Brick's Berserk health regeneration, Roland's Aid Station, Lilith's Inner Glow, and Tediore's Shield could give you an idea of percentage.
From here on are my suggestions on some new vials;
Faster Bullet Velocity vial. Tremendously help Pump Action/Semi-Auto Sniper Rifle specifically, and other type of weapon generally to make sure the projectiles hit instantaneously the moment you pull the trigger. Maliwan's Tsunami, S&S Munitions' Serpens, Torgue's Redemption, T.K's Wave's Shotgun are some that come to mind. Just don't mix it with other attributes, as some weapons (Maliwan's Rhino, Vladof's Mongol, Maliwan's The Roaster and Rhino hybrid) benefit greatly with a slower projectiles.
Faster Reload and Equip vial. As the name suggest. Jakob's line of weaponry would benefit these the most. Also, you can throw in Faster Weapon Swap together in the mix, as there is no harm in that, so why not?
As for the Phoenix effect, I don't used it much. 2-3 times tops, even when playing as Brick. I don't know maybe the constant effect, or the radius, or both that kept me away from loving it. Maybe a little tweak on its activation (damaging, or killing enemy) as well would got itself some love it deserve. However, my cousin didn't think so. He thinks it's cool and all, but he's playing as a long range Mordecai. I don't know what to say.