Wolf spawns incredibly low

The issue is that untamed wolves can despawn (contrary to what the wiki says). Moreover, they count towards the passive mob cap, and since most passive mobs don't despawn, the passive mob cap is always full in most worlds, preventing wolves from respawning after they're initially generated with the terrain.

This would probably be fixable just by preventing wolves from despawning.

(Ocelots actually fix the problem a different way – they count towards the hostile mob cap, despite being passive, and since hostile mobs despawn routinely, ocelots can respawn in their place. It doesn't make a huge amount of sense, but it works, and it also allows more ocelots to spawn if the original inhabitants are tamed or killed.)

Cannot Reproduce
Keep in Mind that they only spawn in certain biomes (Forest, Taiga, Mega Taiga, Cold Taiga, and Cold Taiga M)

@ChoclateChip Cookie:
This is not true, passive wolves do not despawn since Beta 1.8, only angry wolves will.