pawsplay
Hero
What monster design from 2e? That was the entire point of 3e was that we actually finally got any sort of mechanics for designing monsters. In 2e, there simply were no rules for how a monster was designed. It was all just make stuff up.
In 2e, monsters had unified mechanics. All monsters of a given HD had the same attack matrix/Thac0, and saving throws follow a regularized theme. They had few special abilities, and these would be spelled out in small paragraph formats. 2e introduced the one monster, one page format, as well.
3e, by contrast, assigned monsters a bunch of feats, whether they wanted them or not, and gave monsters ability scores, which could vastly affect their capabilities, but weren't directly taken into account by the monster design rules. Insofar as they affected the creature's capabilities, they had to be reverse-engineered.