Less than 24 hours...

[Eidolon]

You mean like all the ex modes?

Garuda, ifrit, Titan ex during the relevant cycle were a decent challenge, particularly because weak links could cause wipes. They weren't on the level of coil, but they offered a fun challenge for the mid level with decent rewards.

Shiva with a good tank is basically w loot piñata, beat only by t2 enrage