This does appear to be the case, yes. Losing in 2.5 days by an innings and 150 runs to the next worst team in the league would suggest that they are total toss.
It's hard to see Sussex escaping with anything from this one, such is Northants commanding position now. They STILL have four wickets and only need 250 runs or so to take this game well out of Sussex's reach.
This.
I think we all know that in 24 hours, Northants will be 420/2, ready to smash our feeble attack to all parts of the ground on the 4th day morning, with a view to skittling us for well under 200. In fact, for this reason I'm quite tempted to stop following proceedings from this point onwards.