I dont think the problem at United has really been the managers, it has been a combination of the manager as well as the people above and below ie. include the Chairman and the Players too.
The chairman - ET is notorious for being impatient with all his managers - you cant really argue that point after so many managers in so few seasons. He needs to step back from the edge and let his manager (whoever it is that week) get on with the job. No manager can concentrate on the job in hand if he has to keep looking over his shoulder every 5 minutes to see what the chairman is saying or doing.
The Players - McCall brought in a few highly paid individual players and that is what they remained - individuals. The players have to shoulder a fair bit of blame for turning up for work but not putting in performances they were capable of. Its a long time since DUFC were a 'team' in the way that ICT, St Mirren or Falkirk are. Whilst I have no love for the Buddies or the Bairns, it looks like the time spent by all three teams in the SFL have helped nurture a team spirit and a work ethic that have seen them all look safe from being relegation fodder in any of the last 3 seasons while DUFC have looked like it every season no matter who was in charge. Maybe a spell in Division 1 will help some of the players come back down to earth ?
The Manager(s) - We should perhaps give Brewster a little credit for getting rid of some of the overpaid guys that had come in before he went to DUFC, but his naivety shone very brightly when he couldnt replace them and then seemed fixated on bringing several players from ICT instead of looking at what was also available elsewhere when we refused. The upshot was that in the end, he signed virtually nobody. I think the DUFC job may have been too much too soon in terms of the size of challenge he was ready for, especially with an impatient chairman, and he may prosper under the watchful eye of Leish at Dunfermline.
Levein : I hope he knows what he has let himself in for ? He didnt relish the thought of a meddling chairman when he left Hearts, will this job be any different ? His pedigree for the Hearts job came from a good spell in charge at Cowdenbeath, and he hasnt really done that much at any other club he has managed. Lets not forget that McCall was also a successfull manager at - then Division 1 - Falkirk on a shoestring budget and was seen as a saviour, and we all know how that ended. I wish him luck, but fear he is going to need a **** of a lot more than that.