i think its the opposite. In SC you need more skill in playing your char, better timing, positioning, and you have to be more aware of what you teammates are doing. The content of smallscale is generaly more challenging than big scale. And therefor you will encounter more high skilled players, who got a biger understanding of the game and their classes, wich makes the gameplay more challenging.
when i talk about building or joining a group, i doesnt has to be a full 6man with perfect setup. when you que with 3 people, in 1-1-1 setup, you allready made sure, that your group has at least one tank, one guarded DD, and heal! No matter which random classes build the other 3 man, your group well be much more valid and useful, probably you will carry the whole group through the SC. Even when you are only DD and tank, then at least you can be sure to have a guarded DPS, who is able to do his job, and wont melt instantly. No matter what, every combination of 2,3 or 4 people, is still better then a solo que!
The problem with ranked SC is not, that a group is scared to fight another group. This is what happens every time in SC, cause in many rounds you got 1 premade on both sides, and 1 random group. The difference is, that Ranked SC is very competitive. And you only want to do it, if you can bring a competitive setup by yourself. Not every setup is perfect! When you got 6 guidies online, and 3 of them want to play their DD... well, then you build a group with one tank and 3 DPS, and go for it. Or maybe only one healer is on. Ok then, lets play a bit more passiv, but lets try it with 1 healer. Or you got 2 tanks of same kind.... and so on and on... Thats totaly ok for regular SC! You ca do it succesfully and have fun. But you would not que a ranked SC with these kind of setups, cause its not competitive! When you encounter a 2-2-2 competitive premade, you will loose for sure, just because of the suboptimal setup.
Not every Guild can bring a perfect setup every evening. Most of guilds cant even bring a full 6man every eveening! So they que with 3-4 poeple. And STILL, like i explained above, this is far more better than que solo, and your chance to win will increase drasticly.