As stated above the OT should be kiting pre split and no one should be kiting post split. Time the split so they have 0 stacks and your OT is in position.

When is the split? 66% hp. How can you tell when that is going to happen? I know a guy who literally took a piece of paper a long as the focus target's health bar and drew % marks on it then taped it to his screen. IE: whatever you need to do to know when its coming.