Test+ODI+T20I Combined:
443 wickets at an average of 20.46.
Thats serious numbers right there. He's well on his way to All Time Great status. In terms of all formats combined he might be an All Time Great. But purely a Test cricket All Time Great, for me...not there yet.
For me, an ATG in longer and shorter formats both. I have seen enough against top oppositions of his era and that too when playing away in tests. That's harder for bowlers and batsmen both. I saw him enough in tournaments. I don't follow shorter formats outside of tounaments. There comes a point where you say, with quality and longevity, it's enough to go down as one of the greats. He has passe that point for me. Understandbly it may be different benchmark for different fans. As some one said in this thread, there is no factual ATG level. It's all subjective.
Not enough to be a contender for the top 5-7 spots yet in the test format. 50-70 more wickets against top sides then that discussion can take place, not now.
Many fans don't account for the fact that he is not going to play against Pakistan. One less opponent. Also, if you are a top class bowler in all 3 formats then having a yardstick of 300-400 tests wickets is too harsh. In 3 format era, anyone who is a top class in all 3 as a strike bowler is not going to play as many as some test specialists played in older era. Some players did play lots of games in both formats and maintained very high standards, but that list a short one.
Sure, some longevity is needed. Some one shared earlier here that for all asian pacers, he is among the top 3 pacers in number of wickets outside of Asia. So not much to see in longevity outside Asia for him. At home he has lower number of wixkets. I think 40-50 wickets at avg of 17. Get another 50-60 at home. He is avearging 9-12 against BD/WI/Zim, but he has not played much against those teams and not likely to play much due to all this tier talk. Otherwise cheap wickets against them can boost volume, but I don't think it will make him a greater bowler. That's just volume and it may help some fans who want to see volume.
Realistically, he will play majority of games against the top 4-5 test sides of his era.