Bane target limit

[Yenn]

Frequency: Always
Class/Level: 50 Summoner
Party or solo: Party
Steps:
1. Group five or more monsters together in a tight cluster.
2. Target the monster closest to the center of the group and apply Miasma, Bio, and Bio II.
3. Cast Bane on that monster.
4. Notice that only 3 monsters were affected by Bane, even though all monsters were in range.

This is especially noticeable in Turn 4 of Bahamut's Coil, where you have 6 or more monsters stacked together during the first and fourth waves.
It will never spread DoTs to more than three monsters; it seems to give priority to spreading to the monsters with a lower letter by their name. For example, if A, B, C, and D are in range, D seems to always be unaffected.

This may be an intentional limitation, but the tool tip says nothing about it.