Irrespective of how seriously established players take county cricket, it used to be a great way for up and coming Australian players to round out their education, by playing in conditions where the ball swings and seams a lot.
I recall Steve Waugh going there in the late 80s, Mark Waugh too. Tubby played a year or two in League cricket as well. Even AB played in the mid-late 80s when he was arguably the best player in the world. These days the international caravan seriously inhibits players wanting to play county cricket, while the lure of T20 riches also seems to mean players' priorities lay elsewhere.
The moving ball seems something of an alien concept to a lot of our batsmen these days.
TBF guys like Steve Smith and Phil Hughes have played in England. Reckon Khawaja should go over and play since he's not a big part of the OD scene yet.