Pay attention yourself. The glitch is pervasive and is experienced by many players. Teams I have easily defeated with lower-modded squads won’t fall to my strongest. Encounters I defeated easily earlier on now become impossibly hard. The issue has floated among various individual toons that suddenly become impossible to kill, such as when any team containing Nest that was put against Traya in the Sith Academy event would result in Traya and Nest trading endless strikes with neither being able to prevail. The type of problem has popped up with various toons at various times over the course of the last couple of years as the encounters got more complex. This time it popped up as effecting whole squads in the Conquest Event. The algorithm system used to calculate damage versus probability of counter to damage has clearly developed some sort of instability. Sometimes a toon with an annihilate capability can break the bug because it’s probability of hit is near absolute, but sometimes even that won’t work.
The facts that so many people are reporting this issue and that it pops up in so many different aspects of the game suggests a deep-rooted coding issue, likely one that will take time to root out. It also appears to be getting worse, at least in the current state. The Conquest event has essentially become unplayable because of it, as reported to me by other members of my Guild after I mentioned it in Chat.
I may or may not be as adept as your august self in setting mods, but this particular issue is systemic, not tactical.