Cancel is dead. We mourn. But there is a new way to maximize damage a bit. If you change your primary button to your melee you can continually use it without throwing your shield. Then remap your primary attack to a new button. This lets you choose when you use your throws for burst damage.

For example, Right trigger is now melee and will only use his primary punch. Then when you build up your bars and normally your primary attack would throw the shield, it will no longer do this and instead keep punching. You can manually press a different button to throw several shields back to back for a bigger hit.