I don't find the coverage of Ground typing to be any better on attack than Rock. In fact I find it much worse - Stone Edge can hit Gary, Dnite, etc for SE damage and since the moves rework it's near impossible to dodge on defense. EQ doesn't hit any of the top tier defenders for SE damage, except Ttar and other Rhydons.
Yeah you can use MS/EQ in the mirror matchup and against Ttar but there are just so many faster + better options. I find myself using even RS/SE Rhydon way more than MS/EQ.