Except 2 slots doesn't get close to unslotted Seeds, you need 2x accuracy and 3x recharge SOs to have a power that still has a > 50% longer recharge than base Seeds of Confusion.
I don't like comparing Seeds to Mass Confusion because they aren't really the same utility. Seeds is you "up most spawns" control power, in Mind, that spot is taken by Terrify. The problem is that Seeds mitigates 100% of damage to those who are affected by it, while Terrify does not.
Control power sets are really hard to compare 1-to-1 because of how different they all are. Plant is an excellent control set, but it has 3 AoE controls that mitigate damage (one being a sleep). Mind has 4 (one being a sleep). Because of this, and also the Terrify thing mentioned above, I don't see Mass Confusion getting a significantly shorter recharge. However, I do think asking for a slightly shorter recharge (180 or 210) is reasonable.