Chuckg -
I agree that they CAN fight as a unit very well, but as you yourself pointed out, they usually don't, until they find themselves in trouble - which is the kind of opening a well led opposing team could exploit to make it a very difficult comeback. Let's face it, the JLA can outpower just about anything that they get thrown on the field with(one of the reasons I've never been a big fan of the book, just certain characters in their individual books) - hence they tend to, as a group, fight as if they have that classic Thor/Superman disad - Heroicly Stupid. People with such disad charge blindly into combat ignoring half of their abilities and try to turn every fight into a slugfest. While this tactic works fine against many foes, when confronted with a particularly intelligent or powerful foe, it usually means they get their butts kicked in round one and have to try and regroup. Hence, we get an even fight because the DC people, especially if the JLA is "in charge" probably just try to plow in and overpower the less powerful Marvel characters - who led by Cap, Wasp, Cyke, and Jean Grey fight with an intelligent strategy from the start.