Sure it is you can have a good character with two 12s and four 14's that would be above the norm pretty much. And in any case if you get an 18 it should cost a player that is the maximum potential save for racial adjustments.
With the 2nd Edition rules one could add points I think 40 would be quite good they could have an 18 and still have some extra points for another decent stat. Or just make the 32 points a direct point buy with 1 point per point up to 18. Then 32 points will go farther.
Like an 18 would cost 10 points instead of 18! Want do you want super-characters?
Why not let players choose a point-buy system or a regular 4d6 die roll rerolling 1's keeping the best 3 dice, then assign them. I know this almost always gives a reasonable character but with strengths and weakenesses. And part of the fun is to use what you get for me anyway.
As for your example of no character class you only need a NINE for most of the basic ones, if I had lets say all rolls that are average then you make do. I had one character that was a Fighter/Thief/Wizard half-elf like that. The highest stat I had was a 12 and the lowest a 9 and I made do. And yes he did survive until a dragon ate him. Frankly I find players who think the world ends because average stats or *gasp
* only get nothing over a 16 to be kind of pathetic. And you can always give them a substitute for their highest stat of 16 if they are being whiney.
Want to know my favorite character ever he was a 1st Edition Character AL THE SWAMPER who had:
Str 10, Dex 11, Con 11, Int 3, Wis 13 and a Cha 4. He was a cleric with a leperous disease (not contagious) and not bright but still took up arms and magic against evil. He was bandaged, he was falling apart and he was well simple minded but could still fight. Turned out to be a powerful support character and retired to run a monastary famed for healing and the only player to survive the whole campaign without dying. I just did the best with what I had and came up with a nice character. True most are more heroic leveled but sometimes dice are not kind. And I refused a GM intervention to "fix him". They all said he wouldn't survive but he did.
I even had a nice line for casting his turnings: "I AM AL GO BACK TO HELL!" (channeling the full might of his diety the Sun God RA into the foul creatures).