I completely keep Fracture and ID exclusive to burn phases. If I need to burst something, or burn something down asap like Dreadnaughts in Turn 4, I just toss them in there like crazy. The trick is to go into those phases with appropriate starting TP.

In general though, both are very inefficient skills compared to MNK's native repertoire. If you have TP issues in any instance, the first thing to do is drop ID and Fracture from your rotations completely.