You forgot diplomacy. I usually switch explo for it once I colonized and discovered what I wanted
I agree, Diplomatic is a slightly underrated group and deserves to be mentioned. Reduced warscore cost, cheaper no-CB and truce breaking are relevant for any expansionist game. Cheaper war exhaustion reduction is also nice, no stab hit for breaking RMs allows fishing for random PUs as a Christian country (and PUs are a great way to blob). The diplomatic reputation bonus is the same as in Influence and the additional diplomat is not important in certain situations but it is absolutely crucial in others, for example early game in the HRE or late game when there is a lot of stuff to be done at once.
If there is a situation where taking Diplomatic makes the difference between becoming the emperor or not as an HRE minor, then it is in fact the most powerful idea group a player could take in that scenario (it beats Influence easily in that situation).
Economic is THE best non-blobbing group IMO, which silly as this sounds means it's still strong enough to be viable in various limited blob situations. Crowded or constrained MP for example. Ticking -LA is one of the single most underappreciated perks, and I think people underappreciate just how much spare mana gets developed over a game.
The problem obviously is it competes with admin and religious or humanist, and is an "earlier game" advantage, so it really only slots in if admin is worth skipping... which has to mean a very tight neighborhood. When that does happen, though, it can be #1.
The other groups are not merely poor for blobbing, they are also generally poor overall.
The thing is that Economic also requires a certain size to be useful. I think that for a very weak and poor country that hasn't expanded much, Administrative or Quantity would have a bigger impact on its economy (Admin because it gives cheaper mercs on top of the interest reduction, Quantity due to cheaper and more troops). If the country is surrounded by different religions without having any sources of tolerance, then Religious or Humanist are also better economically.
But I definitely agree that Economic is a great non-blobbing group for anyone who has already reached a certain size. The policies are also great for this. Economic - Innovative or Economic - Quality for stacking military modifiers and Economic - Exploration for maximizing tariffs.