"And I think I can see who's going to do the suffering!"
Majida turns up very suddenly, but you certainly know why she's there; with Pickle they never do explain. I reckon that the win-free series 3 got those in charge worried that they'd made Knightmare too difficult, and so an extra helper was brought in. There should have been a better explanation for the sake of the story though.
Actually, in the end having Pickle there didn't make it any easier for the teams (apart from series 1 and 3, KM had an average of one winner per series, sometimes with an extra win right at the end), so it goes to show that the game never got too simple.
Pickle did help a lot. Even with the Corridor Of Blades, where success hinges on teamwork. And his knowledge of the expanded Series 4 Dungeon (e.g. Dunkley Wood) made the eyeshield footage (one of the most striking innovations of Series 4) seem more authentic.