We SHOULD be getting a 50% drop rate, but at best we're getting a 20% drop rate. It usually takes 4 to 8 runs (with +5 NV of course) to get a key to drop at MP5.
Upon using the Infernal Machines, the drops from the ubers seem to be just as bad. Of course we haven't been able to test this as often as the keys, but from what we've seen they seem to have the same broken drop rates.
Please don't listen to the idiots shouting QQ. Test this, or collect the stats. There is ZERO doubt these drop rates are broken, and it is very frustrating. Please fix this.