I have having the same issue, using spvp scoreboard (my B button). Doesn't happen in overworld/wvw when I press B, just when I am in a spvp match. In general I do not experience lag any other time in the game. This is only since a recent patch (maybe the build in which brought in the last chapter of soto).
Also when reading books, noted a 1-2 second lag in the latest soto story instances looking for the books in the tower and also the books in the wizards tower.
The gem store also seems to have the same issue, but not as bad.