I'm not sure if this will affect anyone other than me, as I think my trap is the only one that relies entirely on this method, but just in case;

My trap is set up so that it drops mobs into a giant pit of lava. The lava is held up by signs, and below the signs are spider webs. The mobs fall through the lava and set on fire, then get caught in the web and burn to death.

EXCEPT, since 1.7, they don't burn to death. I went into my collection point to find it full of creepers, and some more research revealed that they were falling through the lava without dying.

I don't know if mobs burn for a shorter time, or fire does less damage, or webs don't hold them for as long, but, there you go.

Solution, put stack another slice of lava above or below the one you already have and enjoy.

It does still work beag. My trap, with the same method of killing, didn't work either for a while, but since 1.7.2 it's been back up to it's normal rate.

We shall test it! And if necessary add a central lava blade instead of the cactus.

I've been on since 1.7.2 and a quick F3 from above the lava pit still showed a number of ID's loitering around in the collection room/corridor.

I was thinking lava blade, too. Just need to find time to get on and do it. Not exactly the most pressing issue when the spawning room isn't finished!

Could they be remnants of the failed attempt before 1.7.2?