Yes, both Saracens and Exeter are successful because they're a tight knit bunch of players. In the old days Saracens would buy in galacticos, only for the team to fall apart when the going got tough. Brendan Venter managed to weld Saracens together into a real team and Rob Baxter and co have achieved the same thing with Exeter. I'd say Deano is doing something along the right lines at Newcastle.
But Northampton, Harlequins, Bath, Leicester - we all seem to have lost that in recent years and are struggling as a result.