Wat.
In SR players spend the first 10-15 minutes in solo/duo lanes meaning they get a ton more experience being a "duelist".
Dominion games probably have a lot more team fighting but it is a bit different than SR. The map changes the dynamics a ton. Players aren't "filtered" into choke areas as much like they are in SR and the team fights in Dominion usually center around a Turret which contributes a lot of damage for one team. Obviously SR has team fights around turrets too, but not always. SR also doesn't have health packs everywhere, meaning players need to be a lot more conscious about their health. I flat out disagree that Dominion has better duelists and/or team fighters.
Dominion is more about territory control, which equates to mobility and outmaneuvering the opponent, that alone means fighting is a lot less critical than in SR since you can gain territory without any resistance at all in Dom. In SR you are forced to destroy objectives and to protect your nexus, this forces players to fight. In Dominion you could theoretically win by just running around the map and cap the fastest. Obviously this would never happen but it CAN happen. SR forces you to at least attack/defend turrets and a nexus before you can win.