The comparison was that good managers can have awful spells at clubs before they establish themselves again - you forget that Clough had a pretty crap spell at Brighton just before Leeds, too. Regardless of how much experience Clough had, his stock was at an all time low. If the internet had existed back then, no doubt such adages like "only good at one club" or "overrated, out of his depth at a big club like Leeds" would have been spewed.
I like to give managers the benefit of the doubt, especially when AVB had an absolutely spectacular season at Porto, reaching some heights that even Mourinho hadn't been able to mirror. His next job will be pivotal, but his experience at Chelsea could be what makes him stronger. I think branding him as a "joke" is ridiculously premature.