Moxie, I'm not clear that Laver surpassed Rafa either! For all-time greats I do give him the edge, but think it is debatable.
To address your points, as far as dominance goes, we're not talking about the Two Andys, who rank in the 15-25 range in the Open Era; we're talking about GOAT candidates. So yeah, dominance is very, very important. This is also why Ken Rosewall is a step below the true inner circle; he had an incredible 20-year Slam-winning span and was a top 5 player for two whole decades - a level of consistent greatness unlike anyone except for Bill Tilden - but he was almost always the 2nd or 3rd best player on tour, never really the best.
As for the international/pool argument, I addressed this with the Babe Ruth comment. We either consider players relative to their context or we try to compare accomplishments across eras. The latter is impossible and, I think, unfair to older players. The former is also problematic, but less so.
Finally, the pro tour. I actually don't play the "what if" game with Laver (and others); instead, I look at what they actually did accomplishment - and that includes pro tournaments. Remember that most of the very best players were on the pro tour; Roy Emerson dominated the amateur circuit in the 60s, and he was a far lesser player than Laver or Rosewall, not to mention Hoad or Gonzales.
EDIT: And while I know pro Slams don't compare to Open Era Slams, and were only 3-4 rounds vs. the 7 rounds of even the amateur Slams, I do think they act well as placeholders for Slams, and are majors in their own right. Rosewall won 23 majors in all, Laver 19, and Gonzales 14. Those are better indicators than their amateur/Open only (8, 11, and 2, respectively).