I think the block damage should be increased, and the radius should be increased as well. By the time you get them showing up, resource collection is not an issue, and having that destructive variable makes the game exciting. I liked the whole being triggered by random zombie hits too, that was a level of chaos on horde night that makes it more memorable. I also think explosions near them, and fire, should trigger a detonation from them. also, if they fall the wrong way, that should set them off. They also should blow up even if dead, i wish they had not taken that mechanic out.
Now what would be extra great is if zombie bears also started showing up for horde night too. Horde night needs to be crazy, and destructive.