Skill cannot be quantified. Since when do channelers in the series wonder about the skill of the Forsaken? They only care about their power. It's the Forsaken themselves who think that their knowledge is superior - which it is. When Moiraine thinks about Be'lal, she says he's strong enough to destroy them without moving from his chair in Tear.

Why does Cadsuane send Alivia off alone with an angreal if skill is important? There is absolutely no doubt that the Forsaken's skill is much higher than any of the good guys, but Cadsuane/Egwene don't know that. All that they know is that they need the strength to defeat these people, a strength that is very rare. So Egwene thinks about linking with Romanda and Lelaine - she knows exactly what Lanfear can do.