Skoll Shorties

To me Orcs and Orgres mature but stay fit for long, land only when at really old age their body starts to weaken and showing signs of old age

I mean Varok and Eitrigg are some of the oldest orcs in the Horde still (excluding Drek'thar) and they're still some of its best. Rexxar I feel like is stronger than both Eitrigg and Varok but his skill is rarely ever seen in battle sadly.

Remember how Drek'thar used to kick some dwarfish ass with two blade and no eyes in Alterac ? And CAIRNE ? Horde doesn't know age.

For Tauren they age like trees if I recall. Though that may have been retconned. The older a Tauren is the stronger they are. This is why Cairne was destroying Garrosh in their duel before the poison kicked in.