You can put pathing blockers, but there are two problems:
1. You can't repeatedly use that destructible/doodad because you are going to get fed up putting pathing blockers over and over again.
2. You can't put a pathing blocker that coincides exactly with the position of the destructible, even using the SHIFT key, so you have to put the pathing blocker(s) around the destructible.
My suggestion is that you should try setting the pathing texture, as LlamaNamedOsama said, since this is a lot more efficient.