If you want to be a competitive player, you go to custom games, and look for other premades.
I lol at that because I don't understand the rational. Because you know your allies are good or something? Being "pro" should mean you can handle any situation IMO.
Much respect to those pantheon and skirmish players with high wins to losses, I have no clue how they do it.
Well, yes, that is the rationale.
Obviously a "pro" player should be able to handle any situation, but to be honest, DG is a team game.
If you want to be competitive, you want to eliminate as much random chance as possible. I.E, you don't want your teams(or the teams of your opponents) to be inherently stacked poorly because of differences in skill, playstyle, latency, etc etc.
A premade team vs. a premade team is going to result in the most competitive, balanced matchup available, and that's all there is to it.
Also, the peope with high win ratios are most likely at least in large part lucky. Due to so many 2v1, 2v0, 4v0 game starts, I have seen plenty of amazing players that have absolutely terrible ratings in Pantheon.