I just recently started playing by Fire Wizard in Mirage. While fighting the Ghultures, I noticed that their damage boosted on me. Is this a glitch? I found nothing on my character to indicate a boost to damage by death monsters.
I think they mean that their attacks are doing more damage than "normal", such as how we have damage boost on our gear(ex.: +11% myth damage on a pair of boots).
If this is what you meant, this is NOT a bug, it's a feature for Mirage and beyond. They had to make the enemies tougher in some way. Ghultures have (30%?) damage boost I think. Either way, enemies have damage boost now, so...yeah. Mirage is where the game gets REALLY nasty.
If it's a case of seeing it show "Boost " when you're attacked, then it most likely IS a bug, because even if they DO completely pierce your resistance, they shouldn't do boost damage to you, unless you're polymorphed into something that takes boost damage from death.