Excadrill is certainly still good. He has respectable stats, a strong movepool, a new resistance, and 2 solid abilities. There will probably be less Sand Rush, but he's a good Spinner option if your team relies on hazards.
Tyranitar is less useful as team support now, but is still a decent mon on his own. He can set up hazards, counter some dangerous threats, or serve as a DD sweeper with his new Mega form.
One of the main advantage that Hippowdon had over Groundceus and Groudon was his ability to provide sand support for his team. I rarely saw Hippowdon in BW, and his usage will probably fall even more in this gen, since dedicated sand teams are even harder to pull off.
Garchomps most sand-reliant set, SubSwords is now almost unusable. 1 turn to switch in, and two for SubDance leaves Chomp with only 2 turns with Veil. It also got a significant nerf in the form of Fairy types, which can put a stop to any Outrage spam. Scarfchomp is still a pretty strong revenge killer.
While none of these pokemon are awful now, theyre certainly weaker, and will most likely consequently see a decline in usage.