3 things which probably cost him quality points
1. Inability to score 500 in any test series
2. Low average against Pak in 2000 when everyone made merry. ( Even Yuvraj averages around 60 against Pak in test iirc )
3. 2004-06 ,2011-13 period
Tendulkar's career average of low-to-mid 30s against McGrath, Donald & Akram led attacks does somewhat indicate his low quality points.
Yes, like you, I also think he never had a stand-alone stellar Test series against all-time great bowling attacks,the kind of attacks where even good batsmen struggle.
I mean, the kind of series performances that say Lara had against McGrath & co in 99 (in that series Lara scored 500+ runs @90+ average, and the next best West Indian batsman averaged less than 30),
or even the slightly less-phenomenal series that Viv Richards had against Imran & co in 80-81 (West Indies innings total never crossed 300 runs in that entire series, Viv scored 350+ runs @70+ average,
and the next best West Indian batsman was tail-ender Sylvester Clarke who averaged 35, no other West Indian batsman averaged above 30).
Although I do believe Tendulkar to be a more skillful batsman (technically) than either Lara or Richards, but for whatever reason his skills never translated in to superlative series-performances against
great bowling attacks. Yes, he would definitely score a hundred against those attacks (that his fans would often tout), but would do little else of note.
I remember Indian batting getting rubbed into the ground by Donald & co. in South Africa in 1997, and an year later against that same South African attack, and on those same South African pitches,
Azhar Mehmood played the series of his life, and Pakistan drew the series 1-1 and came out with their honor intact. As I watched Azhar Mehmood gut it out against the South African fast bowlers, I couldn't
help myself thinking why don't batsmen like Tendulkar come up with sort of series performance against this kind of bowling attack at least once? Isn't it when their team most needs their genius to flower?
Not only will such performances help their team by plain numbers, it will also have a dramatic psychological effect on rest of their team members (as well as demoralizing the opposition).