I would say that Common Sense significantly improves 1.12 and later, due to the development option. For background, I've played one game with 1.12 without Common Sense, and have two in-process (but late game) for 1.13 with Common Sense. I've also played six to nine games with 1.11 and earlier versions.
With the 1.12 game without Common Sense, I ran into two problems. One was the frustration that it was not all that uncommon to have a province with 8 or 9 (or 18 or 19, etc.) development, and to not be able to upgrade it to build a new building that may be quite helpful. So, perhaps it had good manpower and a river estuary - it would make sense to spend some monarch points to upgrade it and get both a market and barracks. Common Sense addresses this. The other was that, as a Western tech group nation in that game, there were times when I had monarch points to burn, even with a couple policies enabled, and more so than in 1.11 and earlier since buildings no longer cost monarch points (in my 1.11 games, I'd spend extra points on lots of less expensive buildings). Common Sense allowed making better use of those times with excellent monarchs.
The subject interactions in Common Sense (which I believe is only available with the expansion, not the patch) also adds some nice additional options to vassals/personal union partners/colonies, which I've made use of at times.
So, for the perspective of someone used to 1.11 and earlier, I'd somewhat lean towards saying stay on 1.11 until you have Common Sense, and then jump into the latest patch with earnest. I'll admit I was skeptical of the building limitations and fort mechanics, but it really does work quite well, when you have the Common Sense expansion. Without it, I felt I was partially missing out compared to 1.11 and earlier.
I think the middling reviews were due to the fact that you could notice the lack of the expansion when playing 1.12 without it (those grayed-out development buttons, unavailable building slots, and useless monarch points), whereas with previous expansions they were really all but invisible if you were playing their patch without having them. Lack Art of War? There's no HRE state religion/religious wars. Lack Wealth of Nations? There's no button to send a fleet on a pirate mission. And so on and so forth. Lacking Common Sense was a lot more obvious, both in the UI and in the gameplay, and I can see why that was unpopular with some people.
Overall, I'd currently rate the expansions (except Cossacks, which I don't have yet) in this order, in terms of how I'd prioritize acquiring them:
1. Art of War. Fleet/army templates, subject casus bellis, subject focus, transferring occupation, and the religious wars are all things that improve nearly every game of EU4.
2. Common Sense. In part because development is so necessary in 1.12+, but subject interactions are quite nice too.
3. Wealth of Nations. While not as common as the Art of War mechanics, peaceful trade transfer and piracy do occasionally have their place, and dynamic province renaming is nice. Trade companies and the Reformed fervor mechanic are also nice in games where they are applicable.
4. El Dorado. TBH I haven't used its features much, but I can see where in a colonization-focused game, things such as the treasure fleets and explorer missions would be fun. It also gives you the Support Independence option, even without Conquest of Paradise.
5. Conquest of Paradise. Its Support Independence option is used in more games than El Dorado's features, but is also available with El Dorado without Conquest of Paradise. I feel its other main features - Random New World and the tribal nation reform - are more niche than El Dorado's, so overall its features would be used less often.
6. Res Publica. Very focused on the Dutch, particularly since the most general feature - National Focus - is also available if you have Common Sense but not Res Publica. Good if you want to play the Dutch, though.
The general focus is I've ranked the ones whose features are most generally applicable higher. The less-generally-applicable ones are good if you plan to play the nations they focus on, but can be passed over otherwise.
