Metal Gears were never meant to intimidate a single combatant.
REX was a bipedal mobile nuke launcher. It can massacre MILLIONS in whatever the hell country/location its controller wants. The Shagohad was a similar story, though not as ready.
RAY was designed to combat Metal Gears like REX. But in the wrong hands, it's just an insanely fast destructive machine. Imagine if someone turned RAY loose in a city. Especially if the one in Revengeance got to, say, Denver. Or Excelsus, which Doktor mentions. Any city would be absolutely devastated.
Can Raiden throw them in the air? Sure. Are they still absurdly scary weapons? Hell yeah they are.
"I would say she saved him, the same way someone that dives on a grenade saves on burial costs." - Alkanshel on FFT