They are worse. At least in 2012 they were.
John Terry spent 80% of his season getting completely destroyed because he couldn't handle playing a high defensive line. His lack of pace was exploited and he was turned inside out by almost every striker he came against, Bent for Aston Villa comes to mind. Its a big reason why his 2014/15 form was a shock because of how terrible he was in 2011/12. In fact, I would argue keeping Terry for so long actually held our team back as we had to play a ridiculously low block to hide his weakness.
Luiz on the other hand had his best season ever last year, was as solid as any defender out there and also a key part of our build up play. He was much better than Terry circa 2011/12. If you want, switch Luiz with Christensen and we clearly have the much better option now.
Cole is closer but he had dropped a few levels from his best and Alonso (Especially in the second half of the season) was our second most important player going forwards as Costa dropped his level and Moses didn't offer the width Alonso offered later in the season. He was our only out ball to stretch defences and scored a lot of important goals. Lets say Cole is better then, that's still only two positions and my point still stands. It's also the area I agree with you that we should've broke the bank for Sandro. Hopefully next summer we do.