I think I recall the briefing for "The Plunder" as referring to an Anemoi as "more valuable than any destroyer". Hyperbole to boost morale, perhaps, but I doubt it was a
complete fabrication on the part of the speaker. Denying one to the enemy while at the same time preserving it for yourself has to count for quite a lot.
Plus, by deploying the Imperieuse early in during the battle at the jump gate instead of setting the trap at Saturn, the GTVA could have avoided:
+Heavy damage to most of Serkr Team
+The destruction of the Medea (a Diomedes is serious business, right?)
+Moderate damage to the Hood
Plus:
+The capture of a Deimos and an Aeolus
+The destruction of or severe damage to four Deimoses
+Moderate damage to the Carthage
+The destruction of THE CARTHAGE'S ENTIRE AIR WING DOWN TO THE LAST FIGHTER. That's not the type of thing that does wonders for a ship's morale, no matter how much Fed ass gets kicked as a result.
And possibly most important of all:
+The need to play insanely dangerous games with the Vasudans to get the GTVA's warships resupplied.
All that for a net gain of two Karunas and two Sanctusesiiae's destroyed (assuming the Indus was mission-killed and will have to be scrapped, which I think is a pretty safe bet). Letting the Altan Orde and Katana off the hook for the moment doesn't really seem like such a bad idea.
Of course the trump card of this argument is that having the Imperieuse jump in and zomgwtfhaxbeamrape everything twenty seconds in to Aristeia would have made for a pretty awful campaign.