Don't be ignorant. Half of those "MC's" you listed are groups, like D.I.T.C., which consists of nearly 10 MC's, and BCC, which is made up of 8 MC's. Big L is also part of D.I.T.C., so no need to mention him twice.
If your argument were to be, say, Guru doesn't fit among Lord Finesse, Big L, Pharoahe Monch, GZA, Raekwon, AG, KRS, Kool G Rap, Ruck, or Nas then you mgiht have had an argument but really you just made yourself fail. Guru is way better than Mos Def, Kweli, Amplive, JuJu, Shadeeq etc. Theres a reason the Gangstarr discography is so enormous, and it isn't all because of Premier. Plenty of his other projects didn't get very far (Group Home, Jeru).
Saying Guru is incredibly overrated is just blatant disregard for what makes a good MC. Listen to any song off of Hard to Earn for proof. Maybe his lyrics aren't as hard hitting as others, but his smooth style easily puts him above most MC's of the 90's. It is true that his style fits so well with Premier's style, but thats why they do so well, but don't give all the credit to Premier.