I can destroy the Songhai, but I also had success with them in my games. They can get a lot of gold even on Deity if you go hunt out barbs and play on the offensive. I think there is more to them than meets the eye.
Returning to the Songhai for my next Deity game is my plan, as it happens...
Sweden goes down. The UA is weird - if you have useless GP's you can gift them and gain some alliances with City States. However, you can easily get couped on the next turn, and boom goes the alliance... I'd love to see Sweden play a huge map with max civs, but that happens so rarely, and lasts so freaking long
The two elements of the UA aren't intended to work in isolation, although the UA is good enough that they can do.
I was on a Large rather than a Huge map in my last Sweden game (random map size, Immortal), and Austria ultimately ended up eating all the CSes I didn't ally, but I had 8 CS allies for most of the late game, only losing one to a coup on the pre-UN vote turn (which wasn't critical - thanks to Austria I only needed 9 votes to win by that point, and had the liberated Songhai, the UN and game-long ally Korea to call on). With most civs I can maintain a select few alliances, but having the ability to generate and gift GPs - and with a UA that makes it prudent to make as many allies as possible to farm the maximum number of GP gifts from Patronage - allowed me to hold onto many more CSes for longer, and more reliably, than I've experienced with other civs.
I down-voted Sweden because I find DoF rare as it is and diplomacy to be somewhat unpredictable. The GP gifting to city-states is marginally useful and to make it useful you'd need city-states that: a) is useful towards your victory condition, because finding a city-state that doesn't really help your agenda is kinda pointless
The only CSes that don't help any victory condition are religious (if you don't have a religion - but even then if you accumulate enough faith you can spend it on GPs in the late game) and mercantile (because while excess happiness is always useful, it's very often not worth the investment at least in the early game). There aren't really situations in which you can't use extra food, culture, or units to good effect. Nor, with the way CS bonuses scale by era, are CS bonuses only relevant in the early game.
In fact with all their similarities, I find Sweden to be a much weaker version of Greece
I have to say I find this bizarre. Greece has simplicity in its favour - its UA doesn't need to be worked at all - but on the other hand, it no longer actually does anything. There's no way in which being able to instantly gain 90 influence is weaker than gaining 2 rather than 1 influence a turn until you hit the resting influence limit. Unless it's changed in G&K (and the wording of the UA hasn't), Greece doesn't give you extra influence, it just has a very trivial effect on the rate at which you lose influence (or regain it up to the resting point following war, trespass, election-rigging etc.). An effect that is now much weaker than it was in vanilla as influence is easier to come by. Whatever the pros and cons of Greek UUs vs. other civs, as a diplo civ it's inherently inferior to Siam and Sweden - and by a long shot.