Don't really do much aero play, but just poking around Sarna and MML, here's my take. The Aegis exists as three different designs: original, Star League refit, and Clan refit. The original base design is from 2372, and was far more balanced. The 2582 refit - which the Clan version is also built on - cut the cargo capacity to overgun the ship. The Aegis's 26th century contemporaries like the Riga and Congress have even less broadside protection (65 and 72 points, respectively) and have less powerful broadsides. So for the threat environment of the time, the Aegis is actually a pretty tough customer. The 2582 Aegis's real weakness is its pitiful thrust, and if you're modeling strategic play, smaller cargo holds and minuscule fuel tank.
EDIT: a word