I have a related question. First off I wanna say I don't have a Ninja in the group, but I do have a Bard and he does what he can, it helps, but it is not enough at times.
After many tests I have found that once I reach 300 or so TP it is better to not use ToD at all or else you just tank your TP incredibly fast thus actually losing more dps than if you were to just use ToD as soon as it falls off.

So the question is, is it better to keep using ToD regardless of TP remaining or to keep a buffer zone after a certain amount for enough of a pool left over while waiting for Invigorate and if so what amount would you say is a good amount, i've been experimenting with 400 as my cutoff and it feels a little safer on progression fights.

Good example is T11 on 2nd phase where once the first 2 nodes are dead and you are focusing on the egg, you generally need the most dps possible and cutting ToD seems better. (This is but one example and not indicating any player deficiency on the mechanics)