I think they are more the victims of bad policy than inadequate training. It also seems that a lot of departments have definite leadership problems (this fact is not unique to law enforcement). Personally I'm not sure there is any such thing as being over equipped. But then if it was up to me I'd roll the M110s with every SWAT team.
There also seems to be an attitude issue with some SWAT officers; an over confidence in their own ability to assess a given situation that I've also seen in some ex military guys with 36 in their MOS. This leads some of them to misjudge certain types of situations, and seems to encourage an affinity for homo-erotic hair cuts.
Leadership is clearly the issue. But bigger/better/more toys can't overcome bad leadership.
