Rainemard casts EnAero when fighting Siren

Platform: Windows 10
ISP: Charter Communications
Type of Internet Connection: Cable
Internet Connection Speed: 36 Mbps
Date & Time: June 14, 2016 00:46 CDT
Frequency: Always
Character Name: Raot
Race: Hume
World: Cerberus
Main Job: Blue Mage, 75
Support Job: Dancer
Area and Coordinates: Yuhtunga Jungle, F-11
Party or Solo: Solo, with trusts
NPC Name: Rainemard
Monster Name: Siren
Steps:

1. Summon Trust: Rainemard.
2. Trigger Siren to spawn for the mission, "The Lost Avatar", and engage in combat.
3. Rainemard will cast EnAero, regardless of the day/weather or the fact that Siren absorbs wind, even overwriting a different En-spell that he may have had active.
4. Pull at hair while exclaiming, "Rainemard, why?!" as each attack of his heals Siren for ~95 HP instead of doing ~95 HP in additional damage.

This behavior always occurs (tested four times). My best guess is: Siren absorbs wind, and to be sure that she absorbs the maximum amount, her wind weakness is set to maximum. Rainemard needs to have a check to ensure that he does not use an En-spell of an element his target absorbs regardless of their resistance value.

Further testing suggests that the "prioritize wind damage on Siren" issue is general to Alter Egos (although it is less consistent on Iceday); so a general adjustment to Alter Ego AI to check for elemental absorption properties would fix this issue regarding any enemies with similar properties to Siren (absorb element X, -1000 (or whatever) resistance to element X).

Then, an alternate solution could be to change enemies with elemental absorption to have baseline resistance to that element--possibly easier to implement, but a less effective solution for gameplay (such enemies might resist damage they should have absorbed, Alter Egos might still sometimes use absorbed elements against such targets).

This is something fairly common. Most mobs with absorption to an element have that element set to be their lowest resist. I'm fairly certain this is done on purpose so that 1) much less likely to resist the absorb which would be funny and weird 2) Make you have to be more careful with your skillchains since multi element skillchains deal dmg based on the element that the mob is least resistant to. And of course AIs will be programmed to do the least likely to be resisted

One thing you can do to combat it is threnodies