I second the people suggesting toluene as a solvent. I always used Pd(II), not Pd(0), CuI (it should be grey or colorless) and did it under nitrogen with heat in toluene. I sparged with nitrogen for a bit before adding the reagents, just to be sure oxygen was gone. I used Hunig's base or TEA, never noticed a difference between them, but I distilled them from sodium before use. Homocoupling is definitely an oxygen issue, either that or you are using way too much copper and it has copper (II) in it.