The problem with this argument is that there's nothing the tahs actually do - the opportunity presents itself because of the sheer numbers of players in this state versus the others.
If you looked at it from the point of view that the Tahs are given a heads start with numbers then they have squandered that head start in every one of the Super seasons - for different reasons.
Based on potential over the long terms they are rank under achievers.
Perhaps a little comparison across the ditch would show you that your definition of success and rating a team as an under-achiever is just nowhere near reasonable. In NZ, the Clan have been like the Cheetahs - occasionally showing a bit of promise but never making the semis (I know, in the '90's one year the made the final, might even have won it, but that's a long time ago). The Hurricanes made the final once a couple of years ago, but lost in the fog. They occasionally threaten to make the semi's. The Chiefs have made one final and got embarrassed by the Bulls, they rarely threaten the semi's. The Blues regularly threaten the semi's, occasionally make it and haven't won since Fitzpatrick retired. So, by your definition, four New Zealand team would be classed as chronic under-achievers. I guess if you looked at SA then at least four of their teams are chronic under-achievers too.
When there are 15 teams and only one winner each year, saying that the only successful team is the one that comes first is setting the bar so high that you have changed the English meaning of the word successful. It does sharply highlight just how good the Crusaders have been that half the time they win it and almost every year they are in the final. But a couple of years they only made the semi's, so maybe they are unsuccessful too.
Your Shute team hasn't made the semi's in my memory, so they're under-achievers too.
Any team that consistently makes the semi's year after year are not under-achievers. The Super comp is a bloody hard comp to win. Everything has to go just right all the way. A big injury toll and you're cooked. Injury to one of your key players and you're cooked too. Link has won one and made the final two other times. Is he an under-achieving coach? Not on your life he isn't, despite him coaching for five or six years to get that.
If you want to single out under-achievers in Australia look to the post-2004 Brumbies or the Force. The Waratahs haven't won it yet but they've gone bloody close twice now and it won't be long before the injury Gods give us a break. Rewatch the first Reds-Tahs game from this year and then tell me that Tahs team wouldn't have given the Reds a far tougher examination than they got from the Saders this year in the final.