I'm using a HTC One X with stock ROM.
I am using the block number feature built into the HTC dialer. When the CID matches the blocked number they get a special tone and the phone does not show any notification that the caller had rang.
I have setup a profile with triggers on incoming call events of any number. When these blocked calls come in they still trigger the event but there are no way to ignore these events.
A possible solution would be to allow an inverted rule for matching phone number.
Another method is to either check if the call is blocked (may be HTC specific) or allow matching and inverting of contact groups.
Phone:
- HTC One X
- Android 4.2.2
- HTC Sense 5.0
Tasker