Anyone who considers the Leviathan weak is obviously forgetting the maybe 1 time he had to fly against one. Sure, we see them getting munched up by absolutely overwhelming forces here and there, or getting vaporized by a beam of irregularly high power, but the things are harder than a brick for their size and pack 4(!) anti-fighter beams with at least 2 covering any direction besides directly fore and aft. They are slow, but since cruisers are primarily defensive warships by FS2 anyway that's not as much of an issue as everyone seems to think. Convoys can move as quickly as the slowest ship, and the likelyhood of a Leviathan lasting through escort duty are pretty high. The Aeolus lacks the armor of the Leviathan (does it even top that of a Fenris?), which is the only possible reason to discontinue its production.