That's not really a good test. You're taking random smashes/rail shots from different geared players and different situations. I don't know which is best. Like theres not much difference from having 2 or 3 pve armorings in your gear. If you're only looking at expertise as damage reduction, there's really not much of a difference, because the % is so low even if you wear all pvp gear and it DR curves so quickly.
The best way to judge damage reduction is by looking at effective health (the raw damage it takes to kill you from full health). Say you have 20k health and 20% damage reduction from expertise. That 20% damage reduction basically gives you an additional 4k effective health which isn't much (like 2 more average hits heh). I might be wrong about this. They might have damage reduction scale, like it does in WoW, but i don't think it does.
Defensive cooldowns, taunts, guard, etc. give more damage reduction than expertise, thats for sure. Damage reduction is also stronger than just looking at effective health, because it also means less globals and resource from healers to top you off and a bigger effective health pool means you are less likely to be gibbed also. Kinda why full pve gear will probably never be viable just from a defensive POV. The damage reduction from expertise is also really important when its combined with taunts, defensive cooldowns, etc, because the damage you end up taking is really minor when you have say saber ward popped, the guy attacking you is taunted and you have 20%ish expertise.