I doubt any considers an Offensive Linemen getting the back of his leg rolled on as a sign of not being able to stay healthy. Any Lineman in the league would have been injured on that play.
You are right about Guards being less valuable than Tackles. However, Andrews was drafted to be a RT, in my opinion he'll be a great one eventually. Right now, none of these guys is an elite LT. Their all playing Guard or RT. I'm not judging Andrews on college. So far in camps, games, preseason, and talk from his teammates, he's great. Right now I think if you put them all at RT, Andrews would play best. However, if either Carey or Gallery ever make a positive switch to LT than you will be right.