Hmm... the problem I always run into with the Dutch, is that you generally start somewhere with one type of luxury (like 8 copies of it in your expansion area), and a couple of other more unique luxuries. It's actually difficult to consistently trade away your last copy of your primary luxury (especially once tensions get high, and you're literally forced to trade it for 4gpt) throughout the game. Not usually an issue in the early game, but by mid-game, it gets complicated.
Also, what starts out as a +happiness gain in the early game if you have trade partners, quickly becomes a -happiness UA by mid-game, when the AI doesn't have enough luxuries to trade you and you start needing the happiness just to keep growing. I do like the grass start bias (it's really one of the best ones for the capital + tradition). But, without India's UA, the Dutch start running into actual happiness problems by mid-game going 4-city tradition, which makes it even harder to continue using their UA. Do you do 3-city instead like India until Ideologies? Do you run Patronage and keep two CS mercantile allies? Exploration? 4-city Netherlands is actually rather tough to keep up with.
I consider Netherlands toward the top of the tier, but not on par with the higher tier. Compare with Aztec's or Siam's growth bonus for examples of higher tier civs. Or, think of Russia UA is effectively a trading UA that gets an average some 45 x 5 = 225 gold per 30 turns (or 300 gold if you use the 2gpt per 1 resource trick/exploit) resource per city from its UA in the early game (horses and iron), without having to lose 2 happiness... and it only gets better as the game goes on instead of worse, and there's a hammer bonus, which is very nice for early game. On the other hand, despite a better start, I don't think Netherlands is ultimately significantly better than even India (same grass start). The two civs you used for comparison were America, a military civ (difficult to compare, since they are a mid-late game military civ), and Carthage, probably the weakest civ in the tier, very recently moved up from bottom tier. If you instead compared with the other non-military civs in the tier (France, Indonesia, India), Netherlands would look more at home.
Really? I don't seem to have this problem myself. Some spacing might be required, but really, I don't tend to find this particular problem that you have. Though you're right trading away all of your primary luxuries gets a bit harder in the mid-game, that's where secondaries come into play. Honestly, if you liken it to Arabia's Bazaar (Which in itself is more powerful then the UA, it just comes into play later), just think of how often you have issues getting rid of your double resources with that.
If you find a few good trade partners early game (There's probably always one or two that will stick with you throughout the game, not every civ will end up hating you after all), you should be able to monitor their supplies turn by turn, and swoop in once they have a second lux. Trade the 1v1 trade, and watch as after 30 turns, they'll come back to you asking to renew it. It does require some micromanagement, yes, but it's worth the effort. That way, their UA tends to read almost like the Commerce final policy for me in that I get 6 happiness instead of 4.
The key to using the UA well is the flexibility it should give you. Swoop in fast on second luxuries, and from that point on you should be able to dictate whether you want the UA to read "+2 Happiness" or "-2 Happiness +7 GPT". Generally speaking, first lux goes towards getting some GPT to get my economy up and running, second one goes towards countering that happiness loss, and after that it all depends. The map should dictate your way of playing here.
Really, their UA is stronger if you micromanage it. Then the Polder comes into play, and you start racking up food rapidly. You name Siam and the Aztecs as foodmongers. Siam needs to make constant investments to keep the food rolling in, which can be an issue in the earlier game. I'll give you the Aztecs, freaking love the floating gardens. In turn however, all the Dutch need is a decent city site. Those few marsh tiles that'll be in your early rings don't matter, Rotterdam/Utrecht will be working the grass around it anyway until Guilds. If you get a flood plains city, things are even better. This also makes Rotterdam/Utrecht great sites for your Guilds as they'll have huge food producing tiles to counterbalance it without the need of setting up a food trade route.
I tend to play the Dutch with 3/4 cities (the 4th really depends on how many new luxes I can grab, needs to be 2 to make it worthwhile), of which 2 tend to have at least 3 polders within their territory. This is of course once again slightly map dependant, but I find I can do this with reasonable success. Tradition, go tall, and if Amsterdam has polders, Monarchy becomes even more fun. In the mid game, work out how the friend blocks lay, and use the Sea Beggars to wreak havoc on your enemies. It works out very well for me, usually. In the early game, you'll want a slight detour through Guilds and, if you needed the economy boost from your UA, Construction to get both defenses and colloseums up to counteract the unhappiness. Then go right back on path to the Universities.
They're somewhat map dependant, yes, I'll grant you that. They need at least ONE solid port city, and if you see flood plains, beeline a city there. But as noted before, if there's swamps around, the AI loves to leave them alone so you should be able to take them for only slightly worse polders (4 food come medieval is still a lot).
I do however say that both France and Indonesia need more work to do what they want. Indonesia is far more map-dependant then the Dutch (Though the Candi buff helps) and their UU is far too unpredictable and poorly positioned to truely work. France's UA is far more limiting, their UI is pretty good but not as powerful as the Polder (Which, in turn, IMO is probably not as good as the Terrace farm, but still a good second) and their UU is just a buffed normal unit without anything truely interesting, whereas the Dutch have a UU that's on a good tech path and can rule the seas for a good time to come. India, in general, has a UU that comes at a wrong time and an UB that, while not poor, is far from spectacular either. I'd say that the Dutch are above those.
Which is why I'd say they should move up a tier, with the annotation that they're stronger depending on map conditions. I just feel they kinda fall in between the two tiers depending on the way the dice rolls in a 50-50 way, they're certainly better then the tier they're in, but would likely be among the worst of the tier above. Though I'm not quite sure what Portugal is doing in a higher tier then the Dutch...