Del Potro and Tsonga yes.
Berdych can cause an upset against Federer and Murray but he bends over against Djokovic and Nadal worse than Ferrer.
Tipsarevic isn't a bigger threat than Ferrer. I'm sure Ferrer has more victories over the top 4 than Tipsarevic.
He has more wins than Wawrinka too yet we saw the difference in resistance offered to Novak at AO. And as we saw, Djokovic wasn't injured or in poor form, he ended up winning the tournaments with little problems afterwards. The difference is that Wawrinka (and others like Tipsy) has a peak level that can match the top players even in good form, Ferrer does not even if he is more consistent. He couldn't even dictate points on his service games against Novak, it was embarassing to see.
What frustrates people like the blogger I quoted is not that Ferrer will be routined by Novak/Federer in semis systematically, it's that there's no chance of anything else happening, he genuinely can't do any better so it's a foregone conclusion. Djokovic would have had a sterner challenge in the AO semis if you had picked a random top 50 player to play that match instead of Ferrer, odds are he'd have a big enough serve/strokes to get more games and that he could make it great and have a shot of winning if he played his best tennis ala Wawrinka.
Berdych actually beat Novak in a Slam semifinal, and in straights. Regardless of the result, you can always count on him to step up in those matches and at least make it a contest, not leave the court after an hour having won 5 games and offered 0 resistance,