The question is, from a meta standpoint, are the implements treasure or not? Meaning, are they simply set dressing for the bad guys (like gear on creatures) which isn't necessarily intended to be filling the coffers of the heroes? Or are these magic items that are a part of the treasure reward system (parcels or what have you) inherent in the game. If it's simply set dressing, then the DM really isn't doing anything wrong by not letting you have access to it, nor does it throw anything terribly out of balance.
In game, this could be explained in many ways, including that the items are so foully corrupted as to be incapable of good uses. Perhaps, a small reward in the form of residuum could be had by destroying the item (through a Disenchant ritual or similar.)
If these items are included as part of the reward system, where he's not handing out magic items because he's giving you these implements you can't use, yeah... that's being kind of a heel. Additional items should be thrown in to supplement the characters or a disparity might develop between the power of the heroes and the challenges they face.
It really all depends on what the DM is trying to do here.