Is scrum success rate the best general statistic of a scrum performance though? If you have a dominant scrum then you'll probably scrum for penalties more often. Ergo, scrum penalties won is probably a more accurate gauge of how dominant a scrum is. Last season, for e.g., the Blues were ~3rd for scrum success but clear first for scrum penalties won (iirc) and their scrum was an important weapon throughout the season.
They don't have that statistic on the Super Rugby website, but I suspect the Crusaders will be at the top of that metric this season. Especially when they have their full propping corps, which, to me as a scrummaging smooth brain, is quite clearly the best in Super Rugby.