The tank datacron level 6 reads "At the start of each turn, if non-galactic legend Tank allies have 50% or more turn meter, damage they receive is reduced by 75% until the end of the turn," but it is reducing the damage not by 75%, but down to just -1.
In a TW battle vs Jabba with Krrsantan with this datacron, all damage was being reduced to -1 when Krrsantan had 50% or more TM. This would mean my characters were only doing 4 damage per hit, which is not accurate.
Additionally, there were times that the damage reduction occurred in the middle of a turn. For example, when an assist would be called by one of my characters and Krrsantan was near 50% turn meter, the first hit would do normal damage, but the subsequent hits would be reduced to -1, even though they were occurring within the same turn.