For a coach to be successful he needs the full support of the admin of the club. If you assume that the coach is at the wheel of your premiership drive than he needs to be given final say in team recruitment and selection, without interference from administration or sponsors. Conversely the coach must than live or die by his sword.
You can see the success that the Tigers have had, and also the Swans with their "no d*ckhead" policy.
I think that most of the coaches running around would be reasonably successful if they had the right cattle. However stand outs for mine are Bennett, Hagan and Stuart, with Bellamy, Elliot and, given more time, Brown on the second tier. Sheens has obviously had a good year but he was in the wilderness for a long time prior to that.
I think Dessie needs more time to grow into the role and build a team that he wants. It's like most things, experience is invaluable so as long as he learns from this year and improves than we need to support him. It took Sheens a couple of years to turn the Tigers around. I really don't think that any other coach would have taken us much further than we got this year given the quality of our line up.