Lead Casing is a bad choice against human opponents. Most competent opponents would have at least some of those cards, or deal high damage via things like Sniper Monkey or Long Range Rang before enough Armor is stacked to make it non-poppable.
Mass Lead Production can give all of your Bloons 15 Armor for half the cost, making it almost always a better choice in any deck that you'd run Lead Casing in. Likewise, Lead Coating Bloon for 1 less Gold can pile up Armor gradually but give Bloontonium too.
This card's cost and two charges makes it very easy to brick with.