Yeah, the Merc's are not only going fast, but once again going longer, so deffo have more than quali fuel and showing the speed on longer runs. Webber did a good time but came out after the Merc's and has since gone back in while the Mercs are still out and going faster.
I'm still thinking that car is almost awesome but they haven't perfectly got that car sorted in terms of race strategy. Though there is a lot of luck in cars/track. I think the Lotus just perfectly worked out for a 2 stop at Aussie, while other cars were caught somewhere between a 2 and 3, at another track the Lotus will be caught between a 2 and 3 stop, while another car will have to do a 3 stop but will "fit" better, faster while doing the 3 stop and works out better.
Unfortunately it seems to be almost all about tyres + luck with getting into a pit stop strategy that leaves you in a lot of clear air.