Not if the shield increase defense rate by the same % while it's in use. Another thing would be to make, for example the Imps, vulnerable to their own fireball. Since it's something that can be done with the "DamageFactor" in the player's actor definition i guess the same could be done with monsters since they are also actors.I just noticed that it also reflects hitscans, so the best thing would be to only reflect the projectiles from Caco's, Knights, Barons and Arachnotrons. The damage given from the reflect to the monster should be the same as given to you. Forget the 2.5% increase, that would be dangerous on UV and Nightmare
Something like this
DamageFactor "Flame", 2 <==== If i understood the wiki correctly this would make the actor taking twice the normal damage from the "Flame" damage type. For a small % like 2.5 % i don't know what the number should be though.