I do agree that the diplomacy victory is a god tier civ. However, that doesn't mean that all civs geared toward it deserve high tiers. Consider the opportunity cost of not having Greece's UA in terms of gold, compare it with Portugal's gold bonus (throw in a k or two for the nau). It's fairly comparable. Portugal additionally provides much more flexibility since you can use gold on other stuff too so you inefficiently overload certain CSs with influence (by virtue of them having easier to complete quests) less. It makes absolutely no sense to put Greece above Portugal imo. The UUs are not enough to move the needle.