If we ban these cards and let the dredge engine survive, we are committing to banning the next Bloodghast, the Bloodghast after that, and the one after thateither that, or Wizards will simply have to stop printing powerful, graveyard-based cards out of fear of making Dredge too powerful
The halfling can threaten to end games fairly early with plenty of Ring-tempting options in black and white, and nearly all of them cost four or less
Fireglass Mentor's ability cares whether an opponent lost life this turn, not how their life total changed
Noxious Ghoul is a Zombie I always want to be playing, and so running it in this deck is a no-brainer (because he ate the brain already, right?)
There are quite a few ways to get crafty and keep your tokens, too