Bosses are immune to these skills because of the movement speed reduction they both give.
Boss immunities are skill type based, not skill based, so unfortunately I can't pick particular skills only. If a skill, Scorched Earth for example, has 2 effects (a dot and a slow), and the boss is immune to at least one of those effects (the slow), it will be immune to all of it.
That said, Chronowarp still has it's direct damage so it's only Scorched Earth that is completely useless against bosses with immunities. Plenty of the other classes have similar skills that do nothing to bosses too.