I think there is a direct correlation between that twitter league table and how a table of "who is the biggest rugby league club"

More than a lifetime. Youtube did not yet exist as a public service when Bradford won their last title. Twitter was not widespread in public consciousness until 2011 when the begging bowl was first starting to get passed around the Odsal terraces. (Twitter itself is a little older than that, but user numbers started to double every couple of months in the wake of the Arab Spring).

how seriously do the clubs and rfl for that matter take social media? do any have a full time appointment just to run this side of the business, as well as running the website of the club/body?

Thats an interesting and thought provoking view and one which id not considered my self.

Would you therefor deem Salford Wakefield and Widnes as bigger clubs than Bradford?

He has 9k Twitter followers.

That figure must have been his monthly salary!