Part of this problem IMO is that the tooltips are just WAY too vague and under explained.

I like to think I read well, but if you'd asked me before I had read this post, I would have told you that Feint has a 20% chance to apply a Slow. The tooltip literally says 'Slow +20%' and that's all. Only after reading the OP and looking at the tooltip again did I realize that '+20%' referred to the percentage of Slow applied.

If the tooltip properly explained that Feint applied an attack speed debuff to the target (is it 100% application on hit? That's not given either), then perhaps it would be easier to see its value. As the tooltip is now, it's easy to overlook.