I am not a huge fan of any marinade / basting on a steak. You pay a fair amount to taste the meat, not the Jimmy sauce.
When it comes to steak I always do the following. Put the steak in a container add some good quality Extra Virgin Olive oil over the steaks - nothing crazy. Add some Red Wine infused Balsamic Vinger. You really do not need a lot of the balsamic. Let them do their business for 20 minutes to a few hours.
Slap the steaks on the braai and on the final turn drip the left over juices over them.
Once your steaks are just lekke remove from the braai, let them rest for 5 minutes and add course salt.