We're discussing the battle vs the Thalmor? Moot point. Thalmor forces are dented and they reproduce more slowly than Humans. Add to that the Stormcloaks have the Dovahkiin in the event that they're fighting the Thalmor, and the Dovahkiin has both Odahviing and the dead of Shor's Hall.
According to imperial library pocket guide the elves didn't reproduce slowly they reproduce normally but kills them because of their want of purity if they want to they can just stop that killings to repopulate.
And yes we're debating the battle currently, and even if you're willing to bid your time to learn the thu'um I don't think other stormcloaks will agree. Most of them hate the empire because the empire didn't attack now while the dominion are weak. If the stormcloaks themselves wait to learn thu'um that'll be rather hypocritical isn't it?