We're doing fine with the adds. Its the damage that the Concussion Mine is doing and the extra damage our assassin tank is taking that is the issue. Upon reviewing the videos prior to the Concussion Mine changes and what our experience has been running the raid, the Mines are doing several times the damage.
As long as you're not taking more than three ticks to cleanse the mine and
you're not having add problems, it shouldn't really be an issue to heal through it. If the adds are being managed, then your healers should have enough time/energy to top off the raid at all times. If the tanks are swapping appropriately, then the healers will be able to get off the tanks long enough to heal through the mine (if they're quick about getting on the player who is taking ZOMG MASSIVE DAMAGE). All it comes down to at that point is just cleansing it before it ticks more than 3 times.