I just give minions resist all 5 (10 at paragon, 15 at epic). Also, I may increase their damage a tad, especially ones in the MM, because it's often low compared to what an average roll would be for a standard monster of the same level.
This might actually make them slightly more challenging than their XP value at the beginning of the fight, but as the PCs clear them out, I think it balances.
