Let's get right to the hard truth of it all: Andrew Luck is a very good quarterback and the Miami Dolphins are much better off losing every game they have left in order to draft him and fortify themselves at the most important position in football for the next 15 years.
That's a FACT. Winning four games and missing out on both Luck and Landry Jones would unquestionably hurt the Dolphins in the long term. Getting a good QB is 95% of the heavy lifting in building a franchise, and without a good one, the Dolphins are left with nothing.
Now, that said, is it REALLY healthy for a fanbase to actively start rooting for their team to lose? Should you, Mr. Dolphins fan, be pleased with the horrific display your team put on against Tim Tebow last Sunday? Is it worth being a short-term traitor if you know that's what's best for your team?
To me, it's just fine to say you're rooting for your team to lose because, deep down, no homegrown fan of an NFL team ever enjoys watching his team struggle. You might say you're tanking for Andrew Luck, but if you grew up rooting for the Dolphins and pulling for them through thick and thin, your eagerness for them to win a game, any game, becomes an involuntary action. You can't help but want your team to win, even when you wish they would suck.
I know this is true because I root for an awful team (doesn't matter which one for this exercise), and even though I do my best to slag them and give them tough love ("Go ahead! THROW ANOTHER INTERCEPTION! IT'S WHAT YOU DESERVE!"), I know in my heart of hearts that I'll always be happy when they do something good out there. If they score a touchdown, I'll still do my little white-man fist bump. It's ingrained in my very being.
So I see no reason why you can't go ahead and fantank for Andrew Luck. The bond between a team and its fans is often strong enough to make fantanking a superficial exercise, and one that doesn't really affect the long-term relationship you have with your favorite club.
If you're a diehard Dolphins fan, rooting for them to lose isn't going to alter the fundamental urge you have for them to do well. Fantanking is an illusion, a way of deluding yourself into believing that it doesn't hurt you to see your team struggle even though it does. Sometimes, you need that to get through a woeful season, so don't pile on a Dolphins fan toting a SUCK FOR LUCK sign into the stadium. He still adores his team. He can't help himself.