I'm sure this may start yet ANOTHER great debate, but technically...no. Each groundblock HAS to have it's own groundwire ran to it's own groundlub/split-bolt.
Do I agree with that idea? No. Only reason why I'm stating this is that Dish is on a total rampage with grounding as of late and even the practice of groundwires sharing the same groundlub/split-bolt has come under fire.
Not dish specific, but a grounding question since we are talking about it. I'm fixing to put an OTA antenna on my roof and run a cable in down my siding and then through the window. I will probably need an amp, and I'm looking at one with a power inserter so that the amp is up by the antenna. Do most grounding blocks pass that power properly?