First of all, I want to point out Konjiki's guide for netting this achievement, as it is the easiest way of obtaining it.

But, if you want to get this achievement the way dev's intended to, follow the steps bellow.

Your team setup:

- Tamitha
- Sandra
- Dalbert

This setup appears to be THE ONE for doing this, as it is suggested by other guides and I can confirm that since I playtested with different setups quite a bit.
Note that this setup gives you speed, flying and fast aura cast, which is kinda THE build for this game in general.

Opposition setup (1):

- Oralech
- Ignarius
- Jodariel

This configuration of three demons allows us to quickly take them out as they are slow and a bit predictable, and it takes them more than 10 seconds to respawn, leaving us plenty of time to score.

Tamitha should be able to make quick work of at least two of them in no time, leaving you with 3v1 situation.

Opposition setup (2):
- Sir Gilman
- Sir Deluge
- Barker (or any other Cur)

This cofiguration consists of three opponents with tiny auras, and AI seems to want them to go around you all the time, leaving you with more room to outflank them. Scoring with a jump or flying into their pyre with Tamitha should not be difficult.

Choose a method that best suits your playstile, I find it a bit easier to complete against opposition setup (2).

Good luck!