From what I understand Webber was 8km/h down on Vettel through the traps. So Webber was 20km's down on the likes of Hulk whilst Vettel was 12km/h down. May be part of the reason why Webber was just that a fraction further back where he couldn't muscle his way through cleaner.
Webber has had been on pretty aggressive strategies the past two races to try and get positions on the track with pace and passing. Vettel has gone the longer strategies where it was about consistency and cars pitting more than him. It seems either Webber cant get the same life out of tyres or when they are splitting strategies Webber prefers the more aggressive strategies. Based on the past two results I think he needs to consider seriously his ability to pull of China/Valencia results consistently enough to bag points towards the WDC