Because it seems that Recount is the culprit, it's not a GPU issue. It would technically be a CPU issue because the data (Lua) is trying to be processed but something is locking it up for that half second.

Also, if you've got Recount loaded on all of your characters, it's probably only necessary to have it loaded on one of them (unless you're trying to compare some sort of DPS reporting inconsistency). And if all else fails, switch up your DPS meter to Skada or something else unless you require super fancy graphs (which I believe Skada has anyway with additional addon).