Did this solo, it takes over an hour from round 1.
Easiest map i found is Excavation. Behind the spawn point is a ledge, you can stream enemies up the stairs and slowly Move back on this ledge.
I would suggest getting the repeater early, I dont like shotguns as you have to be too close plus we'll be getting the preacher for the boss types.
Open up a few doors which will have Blueprints, if you are lucky you will get the Royce M33 Carbine, it has 3 slots and a 50 rd clip. I would put in a health steal mod richchet and fire.
Then you will need to save up 10 grand. Open the 10k door and inside will be a puzzle with 4 levers. Inside the other rooms you will see these heads with candles 1,2,3, or 4. You really only need to find 2, and then just leave 1 guy alive(mummys are the best as they are slow) Then enter the numers you no and guess on the other two if you are wrong just flip those two in the order. Once you do this right you'll have access to the preacher, which one or two shots the rushers and and the champions only need one shot per weak spot. Use it sparinly as it doubles in cost each time you buy it.
I found cluster bobs(if you have the DLC) or grenades to be the best, also remember to suck souls in with RT from afar. IF you can use your ability and kill as many possible in a clump as you can soul suck and get enough to almost spam it.
Save your heal potions for dying, each door holds 2-4. IF you have a heal potion you can revive, once you come out of the sarcophagus bee line for a new heal potion.
Once you beat the boss on wave 15, the acievement should pop.