Might as well throw in Tuxedo Kamen Rider Mamoru in there. Tuxedo Mask Rider Protect in less moonspeak. Without Usagi for her heart-shaped final attacks that can only really finish off a monster, the other Senshi must either a. have their attack power/competence beefed up or b. have some other form of finishing off the enemy with a super attack or combination move.
Actually this is quite fanon. Every senshi has the confirmed ability to kill. It's just Usagi is the only one with the power to turn people back into monsters without hurting them (which 90% of the time was the case) or kill them if they weren't ever human. She's the safest bet and the only one with this ability. As for the senshi manga and anime confirm senshi can change their supposedly short range attacks into massive city range techniques all the way in the first arc. They just don't usually need to considering they're usually only fighting one monster at a time.
When multiple monsters come to play and they're confirmed to have never been human. They get hit with skyscrapers sized towers of water and sweeping beams of death. Once again Everybody has the ability to kill monsters, Usagi is the only one who can heal and resurrect. So the rest have to limit themselves a lot.
One note that's actually quite canon are senshi changing and creating techniques right in the middle of battle in every verse of Sailor Moon. Because they want to protect everyone so badly they can adapt easily. Their powers run on pure will power.
As a notice for physical strength. The senshi have enough physical strength for a slight jump to launch them into space. As Minami also pointed out in the Naruto section, Sailor Moon crippled by the black crystal, barely standing still had enough physical strength to trash Demande's castle with just a punch.
As for Metallia, I doubt they'll need to use the Shiny Magic Rock. They could just teleport Metallia into space and then Arc en Ciel the fucker. It worked on the Book of Darkness's berserk defense program, after all.
Trying to Teleport Metallia period is the worst idea in the world. At the moment she is really sealed in by the Silver crystal. The attempt would probably give her enough energy to free her pretty early.
She freed herself in the manga by through massive amounts of energy (Everybody who was watching a tv show had their lifeforce stolen by Metallia. Sailor Moon had to use her own energy to revive them,) and got fucking huge swallowing the crystal, Sailor Moon and Tuxedo mask. The anime had crippled her by just using Beryl's last bit of lifeforce to take over her body.
Metallia's weakness of her forehead was unknown by everybody besides Kunzite, and was way too small to attack at the beginning.
Metallia is a creature born from the root of all evil. Her existence is to create as much destruction as possible. Trying to off one planet to get rid of her would probably just make her stronger and probably convince Chaos to reassimilate her when she got big enough which is generally a bad end.
Speaking of which, the TSAB should be really concerned with the Shadow Galactica, enslaving people and destroying planets. Earth shouldn't be on their radar in comparison to her. Canonically that while Usagi was the strongest person in the galaxy with her infinite power of rebirth and her Holy attacks. Galaxia was born with the most destructive crystal.
By using her Shiny Rock to rewrite reality so that Metallia DOES NOT EXIST. In fact, she rewrote the universe to wind time back by a year so that the first season and the corresponding manga arc never happened.
That's fanon in both cases. Manga Metallia was defeated by Usagi, Mamoru and Luna all combining their power and hitting her weak point with the power of the Ginzuishou, the moon and earth.
Anime, Usagi didn't rewrite reality either. She just revived everyone and sealed their memories with her dying wish.