If anything your link backs up his argument. Of all the players Benitez signed, only 7 or 8 of them can be classified as hits. It's also funny seeing the massive £84M net spend when people argued he was never backed by H&G.
He did bring in a fair amount of players but part of the reason was because the budget he was working under meant he had to take a fair amount of 1-2 mil risks hoping to unearth a diamond! If you actually looked at the details you could also see that a very large percentage of his players were sold for profit! Yes there were a few duds, Morientes (but many thought he was great before he arrived), Pennant who again was a fantasypremierleague kind of buy, Aquilani was possibly the worst, although in his 10 or so games won a fair few MOM's. Robbie Keane who alledgedly was a board signing, which does make sense considering Benitez rarely played him and was shipped out the next window. Regardless if true Keane was on fire when bought and part of the reason for Berbatov's and Bent's goalscoring form.
On the flip side he brough Lucas for 5mil, the like's of Agger, Skrtel, Reina, Johnson, who are all mostly regulars still. Great buys in Alonso, Mascherano, Sissoko, Garcia. And made a massive profit on Torres which doesn't reflect in that 83mil net spend (as well as the likes of Kuyt who's 9mil got us years of service but little sell on fee), which incidentally is still only an ave of 16.6mil a year. Not bad considering we had a lot of work to do shifting the French contingent, and you could argue Owen went for way less than his worth due to running his contract down.
Like I said he DID bring in a lot of players...... but a lot were free signings (over 20!) , 6 were less than a mil, and 6 were 2mil or less, with a lot of swaps and undisclose which were in reality likely to be low fees being scandinavian or spanish youngsters. Thats the reason there is so many buys, trying to develop youth and unearth some diamonds because the money was not there to bring in quality in every area.
Still I suppose you can draw whatever conclusion you WANT to see from the link I posted.
Edit Mourinho made 24 signings in 3 seasons at Chelsea, an ave of 8 per season with an ave spend of 75.25mil a season
Benitez 76 signings, an ave 12.6 a season, ave spend 38.1mil!!!! Consider that the net spend is heavily on Benitez side and the fact he could rarely afford the luxury of making a loss, I think he did exceptionally well!