Thank you kindly, FrankNichols for a patch that:

The following patch fixes http://opensimulator.org/mantis/view.php?id=3107 
[^] by changing call from setRot to llSetRot, the later handles 
child prim being rotated relative to root prim in linked set.

OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs

@@ -6286,7 +6286,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
                             return;
 
                         LSL_Rotation q = rules.GetQuaternionItem(idx++);
-                        SetRot(part, Rot2Quaternion(q));
+                        llSetRot(q);
 
                         break;