What does Letang do well besides use his skating to cover his mistakes?
He is deployed in all three phases. He's an excellent skater, which allows to take more risks and cover for his partner's physical limitations. He's very quick. He's the best defenseman we have at the transition from d-zone to offense. He's above-average to elite from an offensive standpoint in passing, shooting, and creativity at his position. He's extremely strong, particularly for his size. He's one of the best pure athletes on the team, and goes stretches where he is playing close to or over 30 minutes a night, which is insane and something very few blueliners can do. He's tough, as evidenced by his playing with two fractures in the most recent series. His PPG in recent years indicates someone who will put up 50-60 pts a year, which is elite for a dman.
He also chases points. He has a bad temper and loses it too often. His inability to consistently play a quieter game in his own end holds him back from the true top end of his position. His mistakes are very obvious ones, which make it easier to seize upon them and laugh/cry. Whether you want to call him injury-prone or not, he's missed a lot of time in recent seasons and that's a problem. His hockey IQ has always been relatively low, and it hasn't substantially improved.
If you think his maximum worth is $5mm per, then we just disagree, and I think you have a very unrealistic view of both his abilities and the market for dmen. If you want to say he's not worth 7.25/per, go nuts. I think/hope he can be the player we saw last regular season, but if he never lived up to the play he showed that season, it wouldn't be "stunning."