How about he always under estimates lesser opposition and refuses to play his strongest team consistently.
That's the way he plays, 'pundits' need to accept it. The Big 4 (and Aston Villa) all 'rotate' their squads. But nobody else gets as much stick as Rafa when they do it. Each team Rafa selects is a team he and his coaching staff believe can beat the opposition.
He has a spine of players that are nearly always in the side. It's the way most (all?) big teams will do it.
He has no idea how to handle the English press and a good majority of his signings are poor at best.
Good Signings
Xabi Alonso - £10.5m
Luis Garcia - £6m - Sold for £4m
Pepe Reina - £6m
Momo Sissoko - £5.6m - Sold for £9.75m
Peter Crouch - £7m - Sold for £11m
Robbie Fowler - Free
Daniel Agger - £5.8m
Dirk Kuyt - £9m
Aurelio - Free
Ryan Babel - £11.5m (even though he's having a shocking season)
Benayoun - £5m
Lucas - £6m
Arbeloa - £2.6m
Mascherano - ~£19m
Martin Skrtel - £6.5m
Ok Signings
Josemi - £2m
Scott Carson - £750,000 - sold for £2m?
Zenden - Free
Mark Gonzalez - £4.2m - Sold for £4m
Nabil El Zhar - Free
Craig Bellamy - £6m - Sold for £7.5m
Pennant - £6.7m - Loan at Pompey
Itandje - Free
Leto - £2m
Voronin - Free
Robbie Keane - ~£19m - Sold for ~£12m
David N'gog - £1.5m
Cavalieri - £3m
Albert Riera - £8m
Bad Signings
Antonio Nunez - P/Ex
Jan Kromkamp - P/Ex for Josemi
Pellegrino - Free
Morienties - £6.3m
Paletta - £2m - Sold for £1.5m
Dossena - £7m (hopefully he will prove us wrong)
Degen - Free
Have I missed anyone?
If you ask me that's a not bad at all. When a player Rafa signs doesn't work out he's not shy too admit he's wrong and sell them. He's also good at signing players for a task, and then selling them on for a better alternative (Sissoko for Mascherano etc).
I'd happily guess that Chelsea's and Man Utd's ratio of good/bad signings are similar but Liverpool don't waste as much money as those.