According to the
JP wiki, this event will be significantly harder than Sandalphon. Most players will not be able to solo the EX bosses. Their attacks do high damage and they use very debilitating status effects such as recovery nullification and ability sealing.
Specifically for the 2 EX bosses:
Blue: Special attack does single-target damage.
Normal overdrive does damage to entire party + ability seal for 3 turns.
Raging overdrive hits random targets 3x, which can very dangerous if these attacks overlap on a single target.
Boss has a degree of debuff resistance.
Red: Special attack damages the entire party.
Normal overdrive damages the entire party and prevents healing (for 5 turns?). Not sure if this debuff is removable.
Raging overdrive does high damage to the entire party.