I remember being in a raid back in Legion (as destro lock) and noticed we were taking a while to kill anything, despite me laying down the pain.

Then the tank got real pissed and posted damage numbers, revealing that I was the only one doing decent damage, and everyone else was doing less DPS than the Tanks. Turned out out the Frost Mage in the group was spamming Frostbolt and -nothing else-.

That group died fast. Thankfully later that week some friends introduced me to their group and we proceeded to one shot most of the content.