Also, if you really want to help balance UB, you need to make his grasp unbreakable. Early game (level 5) it's typically beneficial to not break grasp but later game not only do you end up doing more damage if you break grasp you also aren't as exposed (Hammer Slam).
The reason they gave Grasp Stun Immunity in the first place was because he was supposed to be frozen as well and that was to "balance" him out. Give him an advantage to cover his disadvantage. Since most players break grasp at this point, it's stuipid to give him immunity.
They need to either make it unbreakable unless UB gets interrupted or stunned himself or they need to give him stun immunity. The latter is the easier fix and probably the more balanced one so I'm in favor of that.