I've only done this mission a dozen times or so, by no means am I an expert. Anyways.

I run in to the round room and go into the cubby on the right and hang out there killing the trash until the sarge(?) spawns. Then I kill him as fast as possible with full charged VS FB and melee attacks while he is stunned/knocked down. Seems to me the docs shield doesn't drop till the sarge(?) is dead. Then repeat the same on the doc.

When I solo without buffs, I use about 10-15 health pots per run. Multiplayer without a leach, I use 2-4.

I hit 25 yesterday and this morning before the kids woke up, I joined a multiplayer mission. Bought a x3 buff pack, ran in and did my thing, just as I killed sarge, someone else joined and we both killed the doc. I had 3 gems fly out of the doc when he died. A green and two purple lvl 25 kreiberg gems.

I've never had 2 purps drop from the same mob. Bug? I dunno. But the above is what I did and what happened.

I got so excited thinking this x3 buff pack was super blessed. I immediately ran other gem missions afterwards and only got greens and whites.