This is part of the limitation of the four-color genre. It's pretty hard to do investigation when you almost always wear superhero garb -- and few superhero teams are designed with investigation in mind.
In my opinion, four-color superhero stories almost inevitably collapse when you start adding too much more than emergency reaction and personal melodrama to the mix. Once you have characters doing stuff like serious investigation, undercover work and related activities, the conventions that define four-color superhero comics disintergrate.
I'm not saying that's a bad thing, by the way. I'm just opinioning that once characters start doing "serious" and "realistic" investigations, four-color conventions take a beating.
I've found about half the players like "realistic" investigations (in that comic book/less realistic pulp way of the eventual break with a witness, the threads that conveniently fit, lots of illegal surveillance and breaking and entering, etc., not months and months of hard work). The other half range from being along for the ride and giving color commentary to sitting in sullen silence waiting for the brainiacs to get out of the way and quit hogging the limelight.
This requires balancing things. Sometimes I throw in a semi-related combat that isn't heavy or too plot-distracting but gives a nice change of pace. Other times I just switch over to the non-investigating plyers' subplot(s). And also giving the investigators enough challenge that they need special abilities to get their foot in the door helps because then they start enlisting everyone's help.
Just my 2 cents (again, as my last submit got an error - hope this doesn't double-post, but I don't see another post now so I think it's okay).