Opinions may vary, but aside from the DPP33, no switch can be used as a NEC approved ground.
I believe you may have mis-read the question. The OP stated that the system was grounded before the switch. It sounds as if they are wondering if the DPP44 should be grounded as well. In my opinion, it can't hurt to do so, if it's close to the ground block, but I have not seen or heard anything to say it is necessary to do so.
The ground blocks are between the switch and Dish LNBs.
So I gather it won't hurt to ground the switch also.
the ground path is thru the braiding of each coax cable running from the output of that switch to the chassis of each receiver, then thru to the ground lug on the power cable of the reciever to your electrical system.