As long as i could change my training technique slightly and have the dog focus a lot, it is still capable or anything.
This really isn't correct, especially when talking about a herding breed. A deaf dog may be able to do some up close fetching work, but they are not going to be able to work at really long distances, drive, etc without the ability to hear the commands from the handler. Asking the dog to constantly look at you for visual cues, when you may be behind the dog, or 1/2 a mile away (or more) isn't going to work very well.
You could probably get creative and do something like multiple electric collars on the dog, and vibration on one side means go one way, vibration on another means go another way, etc but now you are depending on at least 3 collars, batteries not wearing out, the collar not slipping and changing position on the neck, etc.
For agility, flyball, obed, etc the dog would be fine. Even entry level herding trials the dog could probably pass. But it wouldn't be suitable for what it was (or should be) bred for, real life herding.
