I killed quite a few punies, too, recently since I wanted to complete milestones I had left half done on earlier visits, eco or not. One thing occurred to me which did not get a mention here, although it is easy to understand but as easy to overlook until you actually use a tool to display your total cost of doing anything: Your expenses for defence are zero, once you have built enough strength that your own regeneration rate exceeds the damage that mob can do. Stronger mobs involve armour and/or healing, and there go your pretty numbers. Try the math for yourself, and see how easily you arrive at 2.5 dpp or even lower once you include everything you spend along the way.
Are you sure about the decay? I'm not familiar with that weapon but most don't decay if not aimed at something.
Hmm, must be something special with that weapon then. As it was changed some time ago and I have not had any decay or ammo loss on "normal" weapons since that change.
Sorry for dumb question, but your test wasn't in PvP area? If not, that's 100% bug and you can report it to Support (most likely they forgot to update it, ""HtT" was closed for some time and later reopened, maybe it was during "no decay/ammo consumption on miss" VU).
