Guild Wars 2

I’m using a Sword & Shield, will I get 10% extra critical chance or just 5% if I rune both of them?

+10% extra critical chance I’m lead to believe. This is not a definitive answer though, and I’d rather you didn’t take my word for it.

http://wiki.guildwars2.com/wiki/Sigil

They should stack. The only ones that don’t are those that add a charge per kill or have a chance to trigger on crit. I believe it confirms that somewhere on the page linked above.