Basically it didn't have a maximum number of targets, so it affected the entire enemy army, not just 24 units or so. Needless to say, with the right ability comboes, it made missile barrage look tame.
Still, what about combining Malice, Ruthlessness, *and* a missile barrage? Even if you don't max out Malice (in short, you have Malice at even 1), if you *also* have researched Ruthlessness and have a sizable number of frigates (at least eight in a fleet vs. fleet matchup, though twelve, at minimum, would be even better, aside from Purge Frigates for planetary bombardment) you can turn even the larger Vasari or TEC fleets to scrap in minimum time. Looked at from the balance issue, I can understand *why* Malice got nerfed down. Because of the nerf, it forces Advent players (like myself) to balance our fleets better.
Besides, Malice post-nerf (especially combined with Ruthlessness, Augmented Defenses, and the Transcendence starbases when maxed) can give the defensive strategem I call "Fly in Amber" real teeth. (Though this is, in fact, decently documented, the advantages of Ruthlessness as part of a defensive strategy are often understated.)
I've actually had the pleasure of seeing what Ruthlessness used as a *defense* will do; just last night, in a late-game TEC assault against my well-prepared Advent "Fly in Amber" defenses, because I had researched Ruthlessness, despite relying entirely on the in-system defenses, an extremely large TEC fleet (one battleship, two battlecruisers, a captial carrier, over a dozen pocket-carrier cruisers, and sundry missile and planetary-assault frigates), got ground to a powder in less than a minute. (The defenses were four hangers, a web of beam-defense and jump-inhibitors, and a single maxed Transcendence starbase.) No frigates, cruisers, or cap ships were deployed defensively at all (in fact, my single oversized fleet was deployed elsewhere). Yet *nothing* got out.