I talked with Jesse Sky (Lead Flashpoints and Operations Designer) about the difficulty of Lost Island and its rewards, and he shared his insight about these questions.
He mentioned that Lost Island is balanced very tightly for a group in Tionese-quality gear, but that because the boss mechanics are heavily execution-based, many players prefer to overgear for it. Small mistakes can easily wipe the group, so bringing Ops level gear is great insurance, even if it isn't required. The loot quality reflects this - players who take the risk of going in with Tionese and Columi gear will be rewarded. Players with Ops level gear are likely there for the Black Hole Commendations right now.
That's not to say that we won't be re-examining gear progression going forward. It just happened that when Lost Island was released (1.2), it made sense to us to offer new players and alternate route to the Rakata chest and Columi main hand while infusing the weekly Flashpoint missions with a bit more challenge for players who had geared past most Flashpoints.
Agree with it or not, this has to hands down be the best response to a question I've seen since Georg Z last posted. The answer tells us what the devs were thinking and why they did what they did.
The community may or may not agree that the content can be completed as the devs say it was designed, but that is far less relevant to me than the meat of the answer.
Please, keep good, thorough, informative answers like this coming!