Suggestion
Instead of mutating specific parts, have it envelop the entire body like a critical state so it can be dispelled (broken) with a certain amount of damage. While this would take away the gameplay unique to Dimensional Mutations, it would resolve many issues.
Current Status
There is a huge disparity between weapon types in their ability to break mutated parts.
Depending on the weapon, a hind leg mutation can create situations where you are practically stuck.