I feel like picking up some go-to scrim partners around our skill level has been really good for the growth of the team. I urge teams do something similar. If you're high open and you're consistently 5-0'ing the other Open teams in IRC, try playing against IM teams. If you're low open and are getting rolled by other teams, try to find teams in similar situations.
If you're playing teams with a huge skill gap because "no one else in IRC" you either should be more patient or add some other team captains, because you'll improve a lot faster and demo reviews will be a lot more effective if the games are somewhat close.