It seems that it's generally accepted that QQR is around 90-95% of the Greats, but in LOCH, he seems significantly below them, namely his encounters with Guo Jing. His first real appearance clashing with Guo Jing at the Beggar's Sect meeting was horribly unimpressive. He used what seemed to be full powered palms, and Guo Jing was able to withstand it. Qiu also thought that he would not be able to defeat him very quickly and was very impressed by his martial arts. The latter fights are even more even, and though Guo Jing usually has some slight advantage due to terrain or something to even it up, it's still pretty far from what he experiences against true Greats.
Against Huang Yaoshi, Guo Jing stumbles taking a palm immediately, and against Ouyang Feng he is pretty much defeated handily anytime they meet. Even as late as the Mount Hua tournament, when he has reached his peak in LOCH (and we assume the Greats are more or less equal the same as when they first appeared as they probably don't improve much in the year or two that LOCH takes places in), once Huang Yaoshi stops going easy on Guo Jing, even though Guo is in total defense mode, he begins to stumble after only a hundred stances. A full powered Hong Qi Gong can knock him down in a few palms, and though Guo took his full powered palm at the end, he was clearly going to lose in a matter of minutes.
Qiu never showed that ability. He always had trouble, and GJ was always able to match him enough to escape, or until help came or whatever. This had nothing to do with cowardice like GWM, because Qiu always knew he was better and was never afraid, he just wasn't able to overcome him the way the Greats easily could. As readers, if Guo were to fight a Great, we know he would lose no matter what, but when he fights Qiu, there's always a chance he can win. I think Qiu, as portrayed and judged by fights we saw, is only 80% or so of a great.