I disagree. Weakspots are not critical hits, they're amour penetration procs. Your weapon skills tighten the min damage variation you're seeing. Assuming you're talking about archery, at 100 archery on a dummy I get variance of around 1-2 damage (obviously dummies have 0 mitigation).
Also, afaik weakspots on archery is not 100% pen. It's 70% however, I'd argue your over-dramatizing doing less damage on a weak spot and if it is, then this is a bug or you're not maxing your archery.