Mandi is one that I'm a bit more on the fence about, we were definitely a much better team with him on the park, but he only really had legs for 60 minutes, which basically meant that you either had to take him off, or basically concede the middle of the park in the final stages of the game, and brace yourself for an errant pass or three.
All these points you make are valid but Mandi does my fudgeing head in with his error rate, inconsistency and low stamina. That's why I'd roll the dice on another import midfielder. You can't build around Mandi. Hopefully on the next roll you get an "Isaías" rather than a "Dani Sanchez". I honestly think A-Rod would be a better foil in midfield than Mandi (not that A-Rod would come back).