Damage after blocker is killed problems?

Lightcell

I have been having these problems with damage when a blocker or person who is getting hit by berserker or other effects that happen when the potential target is killed. Just now I had a card with berserker from Gideon and they died due to Gideons Reproach triggering when they went to block. That unit left as dead but there was some invisible card still on the field that took the damage other than the opposing planeswalker. This is also a problem with the effects like te devils from devils playground where if they also kill the monster during the attack the extra damage is triggered before the monster has left the field, causing the damage to be eaten by the already dead monster.