In 2019, there were 47 relievers with an fWAR of 1.0 or more.
There were 335 relievers that pitched more than 20 innings that year. A true "average reliever" would be about 0.2 fWAR. I would say that an fWAR of 1 makes you a good to very good reliever as teams would likely only have 1 or 2 of those guys.
Only 9 guys had fWAR's that were "very good" according to your scale.
So, 2 great players.
7 good to very good players.
28 average to above average players.
288 below average to scrub players.