The reason the Obama Administration is so quiet is because they have done incredibly stupid and illegal actions that have resulted in multiple murders both here and in Mexico and god knows where else.
They are now trying to cover it up.
The reason Issa is quiet is simple timing. It's summer and most people are on vacation and simply not paying attention.
This is going to get a lot more interesting starting in late September
I agree with your reasoning about Issa’s silence. Add to that the debt “crisis” and now 0bummer’s vacation and it has not been a good time to compete for news coverage.