This topic has been discussed in one of the blogs elsewhere, but participation in this discussion is limited.
Here is my take on this subject:
Hahnemann probably did some experiments with combined remedies. I don't have any cases relating to those. In his later years he realised, that one remedy is enough at the time, and two could not do better than one. This was also the bone of contention when hahnemann was asked to be the dean of Leipzig hospital, -- he only accepted, once it was promised that there will be no combination remedy prescriptions.
but why not -- may one ask -- couldn't a combination of remedies given at one time have effect and be beneficial?
And realistically this cannot be denied.
Only, the problem starts selecting the remedies which should be combined in the given situation.
Theoretically when combining remedies there could be culmination of effects, or canceling out , or completely erratic effects.
Can we know in advance without a proving? NO.
So far predictions have failed about effects of combination remedies, an example being Calc -Sulph compared with Hep-s.
Therefore its up to everyone to decide, whether to work experimentally or to rely on well established medicines.
On the other side it would be very informative to prove some of the Weleda, Heel products containing several remedies.
As for myself, I don't use combinations and have never done so.