My first post was to make light of the situation. My second post explained how a simple duo renders the opponent almost totally powerless. My third post explains the pattern required to even consider taking control of an opponent's creature. And this post is to say how to make it better, in consideration of your previous post.
It's a permanent whose function is only to control creatures with HP less than 5. To make this balanced, I recommend changing it to creatures with an Attack less than 5, so things like dragons remain unaffected, while things that have low attack can be controlled. This would be the first step.
The next step is that the average number of creatures an opponent will have is about 7-8. Let's assume that around 2-3 of every creature summoned will be an attack-type. That means somewhere between 2/7 and 3/7 of opponent's creatures can be controlled for a limited number of turns.
