I am not sure what people were expecting of Sky's campaign if they think this year has been a problem so far. It has been a more consistent start to the year than last year was anyway. If people are expecting stage race style domination it just isn't going to happen unless they manage to recruit Peter Sagan/Fabian Cancellara/Tom Boonen or the next 'find' over the next couple of years.
If they don't get any classic/semi classic wins by the end of the year it will be lessons learned and move on, but I don't see them abandoning the 'core team' idea which means it will be well nigh impossible squeezing them into traditional warm up stage races. Maybe they'll introduce a Belgium camp as well and go and dodge the tractors on the pave for a week or so in preparation.
In 2012 at this same point in the classics season they had six top ten results including a 1st, 3rd and 4th place from two riders no longer with the team this year (Cav and Flecha), with Hayman, Bernie and Eddy having one each.
In 2013 they have eight top ten results from one less race (K-B-K was cancelled, it has been traditionally very successful for the team as already pointed out in the OP) including a 3rd place, two 4th places and two 6th places, one of them in a monument. It's not a brilliant start, but they've done quite well so far in my opinion. RvV and PR were the main disappointments for the team with a 17th and 12th respectively being the best placed riders.
I am also not so sure that simply slotting 3-4 classics team members into TA and PN teams would have provided the riders with any useful racing practice given Sky's usual week long stage race tactic of getting the leaders jersey ASAP and defending it. (Maybe stage 6 TA was classic like but it didn't seem to do Henao much good riding that stage). Despite their 'superior to Tenerife?' stage race training Henao and Kiry both ended up crashing twice yesterday early on in AGR. Stage hunting which would probably be the most useful type of racing for trainng classics type riders doesn't seem to be part of the Sky stage race focus since their domestiques always have to try to save energy on easy/medium stages for use in the 'hard' defensive stages to protect the lead/minimise losses. Henao's two stage wins so far this season were both on super steep MTF's which don't appear much in the classics. He'd have probably had more chance on the old AGR finish.
This leaves the team gaining racing/winning experience in one day races and the Classics focussed stage races like TDU and Qatar thus it will take the team a couple of years to build the necessary experience which seems to be what they are working towards. At the moment if anything they seem to be going too far the other way compared to the stage race model and wasting energy to no effect too early in the long classics with attacks that have no chance of staying away or even riding on the front/side in numbers when not the dominant team.
I am inclined to think that the lack of a 'finisher' is the main thing that prevents them from challenging for wins more, even at this stage of the teams development.
I still have hopes that another year or two of concentrating on the road will improve GT's race craft and positioning, his two 4th places before he started hitting the tarmac regularly this year and his stage win in the TDU certainly showed some promise and he could still step up to be a classics leader, if not in the 'big three' league.
Eddy has had a poor start to the season with injuries and stomach issues compounding this, but may come good later like he did last year. His best is very good indeed but he is too inconsistent due to his physical and possibly mental fragility.
Hayman and Stannard would need a very particular set of circumtances to occur before they could win as they don't have much of a sprint, CJ and Bernie are not top sprinters in the classics company, but in the right circumstances could possibly pick one off. Puccio and Rowe are still young and it is not clear how far they can go, but both have a decent sprint if the endurance is there.
Hilly classics wise, with only AGR in the bag so far Henao improved from 21st last year to 6th this year (in the sprint for 2nd), via a 9th at the Valkenburg Worlds last September, which shows good progression. Eddy and JTL didn't show much in the race even before JTL's puncture and didn't finish, but both had already admitted Henao was leader there. Hayman was the only rider I regularly spotted up near the front before the main selection despite his not really being a climber, and he and Josh Edmondson were the only two other Sky riders to finish the race. Uran hadn't raced for a few weeks (since Catalunya) and used the race as a warm up for the later races.
With Froome and Porte still to be added to the arsenal and the great performance of the Colombians at last years Lombardy I don't think we can write the year off just yet.