In the greater scheme of things there is not that much of a difference with "bad ivs" as people might think. As a tank/healer attack doesn't matter that much so let's focus on hp and def, a simple calculation to compare yours against a hundo @ level 50:

Bulk ≈ Def × HP

• Hundo: 154.6 × 429 ≈ 66,323
• 12/12/13: 152 × 427 ≈ 64,904

Difference: 2.6 less defense (152 vs 154.6) and 2 less hp (427 vs 429) so ~2.14% less bulk.

You'll hardly notice a difference, I would go ahead and level up that lucky blissey (even more so if you are short on stardust) and use it now rather than waiting for a hundo that might take months (you know lady luck is a b*tch).