Some more info is required here:

Which version of Boinc?

Was WCG running first and then you added other projects later or were all projects added at the same time?

Which science applications do you have selected here at WCG?

I am guessing you mean 7.2.42 as there is no 7.2.72 version.

On the version 7.2 clients, when you add projects after you have already been running other projects it will request work from the new projects for a while to balance out the resource share of all projects. This balancing out is not done over just a day or two but over weeks as Boinc looks at everything in the long term.

Also, since you added Climate Prediction and their longer running workunits, your minimum work fetch setting has most likely been exceeded. Just let Boinc run the tasks it has and eventually it will get more WCG work as CPDN will run for so long that it won't request more work after a while.

Not requesting work for WCG or other projects only becomes a problem if your machines are using less cores than you have specified.

You can set extra log flags in cc_config to see who's got work fetch priority. Also somewhere in the project properties screen of boinc manager you can see this. Wcg is currently showing as having a priority of -1.96, nothing to fetch. We used to be able to reset in old the inter-project debts with <zero-debt> too, but does not work any longer since the debt system was dropped. Consequently, to me that is, the project switch setting of 60 minutes has become largely redundant since agents now work off a bunch for one project, then go out to work off a bunch for the next and so forth. The sampled cpdn is the oddball in the house. A single large task can fill all of the buffer, as in one task projected to take 14 days and having 4 cores with a 1 day buffer setting will mistakenly project as if you have 3.5 days per core. Think to have seen some more tuning going on with respect to this project in 7.3 alpha. At least work will be fetched if a core goes idle, that's been with 7.2 and various previous versions.

How many non-WCG projects are you running?