If you think that any of these champions was better than Tubbs in my opinion you are wrong. Stiverne Botha Bentt Seldon Martín Briggs Liakhovich Leon Spinks Maskaev Peter And the list could continue
I think they are a similar level. Nothing on Tubbs record outshines their worth. leon spinks has the single best win on that list. So he probably doesn’t deserve to be on it. You can’t take it from Leon. For one night the world had to accept he beat the best guy out there. Tubbs and the rest of them never did. Not for one night. Not ever.
David Tua only ever beat one man ranked in the top ten (Hasim Rahman), and that fight should arguably have been DQ. Were there better opponents that he could have fought? If not then the win's still have to count for something. I can assure you, that if somebody legitimately beats the best heavyweight contender, I would give them credit if they were a bantamweight.
Hart beat Johnson, whatever the circumstances, so he deserved to be in the fight for the vacant title. Root had beaten Hart previously, so he was at least credible I guess. While the Hart lineage is not perfect, I tend to roll with it, as being the least bad option.
Once you start including alphabet champions, that probably buys every lineal off the list. Just by winning the lineal title, you would have done much more than the worst alphabet champions.
I don’t think Tubbs was reliable enough to string two good wins together. He only fought hard enough to keep a fight close. He just messed guys about. He’s not consistent enough to beat Botha, Stiverne, Charles Martin, Leon Spinks, maskaev, Peter And Bentt in a row. He’d likely beat Stiverne then get knocked flat by Bentt in his next fight. And I don’t think he could ever beat Leon Spinks the night Leon beat Ali. As poor as Ali was when Leon fought him that is still about as good as Prime Tubbs ever was. The guy simply doesn’t deserve much credit. Sure he had talent. He just didn’t have the wins. He was never a the best heavyweight in the world. Never could have been.
There's really not a case for Jeffries being anywhere near this list even if you don't rate his era. At the least you'd have to put him above Corbett and Fitzsimmons. And you'd have to put him over Hart and Burns too. And the criticisms of his era apply even more to Sullivan's, so not rating Jeffries you'd have to put him above Sullivan.
If you put Jeffries on the list, then that is pretty bad for every champion before Louis. Jeffries clearly has the best title reign of any champion between Sullivan and Louis, so that would make the pre Louis champions look pretty bad, even if you had then above Jeffries overall.