No, I do no tthink your coin has a weak strike at all. Compare it to examples that are known for weak strikes and the difference becomes obvious. Yes I agree that your coin is not struck as well as many other '81-S coins, but compared to Morgans of other dates and mints it is struck even better than most of them. And that is the entire point.
Sorry, I thought I already established that I was speaking relative to other 1881-S strikes. That is all I meant.