Here is the total running order on the basis of PreSeason Testing:
Group 1 or Leader Group
Mercedes and Williams; Mercedes has the pace and until 3rd test they were looking like have no major reliability issue but 3rd test changes that and put a doubt on their reliability while Williams is the most consistent pace wise and also the only team with out any major reliability issues throughout the testing.
Group 2 or Just behind leader group
Ferrari and McLaren; Ferrari have major reliability concerns and they are certainly down on power incomparision to Mercedes engines while McLaren were fast in the first test at Jerez but in Bahrain they hit trouble regularly and not shown any signs of development either as Button confirms in his interview that there were no major updates done on the car since the launch.
Group 3 or Midfield's dark horse group
This group has ForceIndia as the major team to do something extra ordinary with the Mercedes engine against Sauber's Ferrari engine. ForceIndia has posted good times in the early days of testing but then they also came to a halt as other teams improve.
Group 4 or Backmarker group
There is only Marussia at the moment in this group with Caterham having a really difficult time with respect to their both engine wise and aero wise. Marussia could score their first ever point if Renault teams continues struggle in the early races and many retirements expected at the season start and first 3-4 races they only need chaotic race with max reliability in contrast to others.
Group 5 or Renault group
This is most amazing group because it is consisted of only one engine manufacturer supplied teams and that is Renault. Renault have admitted after their first test that they are behind schedule with respect to other engine manufacturers on development side and needs about 20 weeks to reach that point where other manufacturers are at that moment. So even if we assume that this comment was a bit exaggerated to avoid the burden from their employs it is quite clear they have trouble with the engine especially with the cooling components as they were not able to complete quite a few laps before blowing up.
But in the second and third test there were signs that they could find a workable solution to allow their teams to compete in the races between the recovery period. Although their major customer RedBull which are supposedly their factory team too have suffer more problems in the 2nd and 3rd test too. While their second major customer Lotus only started testing from the 2nd test and are behind in car development as Grosjean admits after the 3rd test. Caterham and STR have completed quite a few laps in 2nd and 3rd tests but without any significant improvement in pace.
RedBull who are defending their both titles this season have a long way to go before it could be think that they are in anyway a contender because at the moment it looks like the car could be fast but its way too unreliable although they have check 2 different solutions in the 3rd test with almost same result solution 1 is completely disaster and solution 2 could work but is not going to make them defend their titles.
Overall, the general consensus is that FIA are idiots when they impose a 5 engine rule for full season of 19 or 20 races especially considering the fact that the engines are completely new and have not raced before so expect more engine related penalties in the middle to later part of this season with may be even the championship been decided by reliability. Expect Renault to make a recovery around Barcelona GP in May, RedBull could contend for some race wins if the car remains reliable but defending title is a bit too far. Williams at the moment has the car that could bring back their glory but they have to ready themselves for a upgrade war where staying ahead is the only way to remain in contention. Ferrari should prepare for a clash of titans if the car doesnot deliver then all hell will broke loose from Alonso and Kimi could be the target.
Last but not least the fears of the next generation cars being slower then their predeccessors is not going to happen as we have already seen that these cars are doing laps in the same time frame as the 2013 cars did in Bahrain GP and these cars are not refined at all.