I've looted 3 ESI with 60% eff
I know some others have looted ESI from small mobs with around 64% eff (edit: Kerb dom, longu old)
'Optimal' loot is DPP oriented and not Eff. (I.E. All crits with swine dlx still has good MU comp) So, higher FB/crit dmg will help you loot more MU vs. Shrapnel. Now....don't mistake this for a 50ped Shrap loot magically changing to an ESI because you shot all crits, the ESI stil needs to be available. More like, ESI was going to drop anyways, you shot it with all crits you got a 40 ped ESI and 10 ped Shrap, versus no crits you ended up with 25/25 split.
Dpp isn't making them magically drop though I can assure you that, just controls the MU portion of the loots size. If your Dpp is terrible, you can override all MU and get only shrapnel.
Also this is shared loot, I can almost be certain in this case, that the users dpp/eff had no effect on the MU they looted. TT value? Of course it improved, they're spending less per damage and loot is rewarded here based on damage. It's entirely possible Vodka just had great DPS and was more inclined to loot the item.
In fact, im certain their setup had nothing to do with looting the item beyond anything but DPS and distribution luck. As the contents of the loot were developed by the collective average dpp used to kill the mob.