It would certainly change a lot, which is what testing is for. A card to balance the change should also be considered. Or many nerfs can be made, such as two shields with 75% proc efficiency and 50% defense status (rounded up). So a spine tharapace and a permafrost would give 2 defense and 75%^2 poison proc and 75%*30% freeze proc. I still dubscribe to a fire card granting a second weapon slot, and have it get momentum. Oh, see? momentum passes both shield, and is common enough as is. Bam, balanced.