Tempus is interesting Advance insurance for Aggression, something only Justice has usually had. Everyone knows the feeling of stabilizing a game, maybe even turning the corner and starting to pile on the damage, only to lose on the spot to that extra scheme from the encounter deck... Tempus represents a satisfying safety valve for that scenario, and since she's an ally, she can also emergency block - adding a layer of protection. I recommend only using her interrupt when you're truly about to lose the game since the extra encounter card you deal could be just as bad if not worse. In the early or midgame, she's totally fine to chip in 1 THW/ATK and then block, which gives her a high floor. Most cards I evaluate on a resources-to-value+speed measure, but Tempus operates on a very different axis that I might call worst-case-scenario-mitigation, and to that end I think she's a very powerful card.