AD&D 2e Hyenas had more HP than Gnolls, 5e is the opposite

So in 2e, Hyenas had 3 HitDice (3d6HP ~= 10.5HP), and Gnolls had 2 HitDice (2d6 HP~=7HP). Orcs had 1 HD (1d6~=3.5HP). Hyenas did the same dmg as ~orcs and gnolls, too. 

There were even Hyenodonts which were like giant hyenas with 5 HitDice (5d6) and 50% more dmg. 

5e DnD is the complete opposite, with gnolls averaging 22 HP and hyenas avg.ing 5 HP. 

What does this mean? Well, hyenas were tougher, I imagine them darting in and out and not such an easy target. Now in 5e, it's like the humanoid style monsters are just automatically the important guys and are better than regular animals. Also means fireball doesn't kill squat in 5e compared to 2e, but we already knew that. Even high level spells often aren't guaranteed to kill basic 1/2 challenge rating things like gnolls. It does grate.