Comparison: Wyrmling dragon and a cat

[Delta]

Because, as we all know, creatures of the same size category should all roughly have the same level of combat ability, despite their Hit Dice, creature type, and stats.

Well, admittedly Skip Williams wrote an article detailing the ranges that every monster type/size should fit into. And if you look at his specification for Dragon sizes (already inflated compared to other types) -- all the Dragons break those rules. So something's definitely amiss.