Not sure how you can discredit a manager just because one player has been excellent. If so, how about Jol without Keane(2006)/Berbatov(2007), Redknapp without Defoe(2010)/Modric(2011)/Adebayor(2012), Sherwood without Adebayor(2014) and now Pochettino without Kane ? Or how about the past Spurs teams without Klinsmann(1995) and Sheringham(1993) ? I think just because one player has been the most influential, it doesn't mean the team would have done badly without him. We would have had other players in their place who would have done similiar roles.
Frankly, I thought Bale was more of an hindrance than help to the team under AVB in 2013. The other players simply relied too much on him for goals. I think without Bale, players like Defoe, Sigurdsson and Dempsey would have stepped up to get the goals. The only thing we would have missed is Bale's long range wonder goals !