Every patch of EUIV, and most other PDX games, has been a "total dumpster fire" according to some. Just the points of concern and volume of discussion changes. That is unlikely to be different for 1.6, 1.7, 1.8, etc. Until EUV comes out and we can start the whole process again.
I'm not familiar with other PI games, but EU IV's patch history has been very sour and its complaints are unusually bad...and unusually justified. Very few patches get this kind of reception consistently. Despite that I'm not a big Civ V fan like I was IV, I follow it. It was *trash* on release and steadily got better in its patches and expansions, and the impact on the forum was very observable over time; dissent decreased markedly. Your typical shooter patches barely get noticed by the masses. Patches in things like Starcraft II, while debated and sustaining circular arguments over balance ad nauseum, were and are generally well received...especially when compared to this.
The devs aren't tweaking the game here though, and that's a contributing factor.
They're introducing wholesale changes to core mechanics without anything in the surrounding mechanics that helps those changes make sense (alliance on "great powers" --> great power flip flops like crazy early and is really lenient. That didn't used to matter, but it's diplo-crushing now). That there are no compensating factors for changes like this lend credence to the suspicions that design intent is either unknown or flip-flopping. The ostensible reason for this change in particular is to break up late-game alliance webs, but what it also does is directly double-buff AE (less sustainable alliances to mitigate it) and shatter early game alliances as virtually ANYBODY can temporarily meet the piss-low criteria for "competing world power", even stuff like Bahmanis in AI hands after taking 2 provinces. Horrible relations between AI in droves due to the broken alliances, and the player is forced to hate the AI when it breaks alliances over that. That's...not exactly the end goal the devs described to us. Many mentioned this as an issue in the open beta.
They're making patches surrounding a broken feature (coalitions) that address something about it that is not and never was the central problem with it (AE), something that was pointed out many times since the game's release.
MP still CTDs and de-syncs, something that's virtually impossible to observe with quality multiplayer net code, this around half a year after the game came out. Civ V holds the previous record for long-term poor MP connection issues "that I've observed" at about one year --> is that going to be broken?
And then, with all of this stuff going on, bugs that get reported in open beta like "newly acquired vassal doesn't drag its master to war" makes it through 3-4 beta iterations and straight into an official release, right along with the AI declaring war on nations it physically can't reach.
So yes, this patch will get a fair amount of well-deserved vitriole, as did 1.4 with mid-war adding of protectorates and the complete destruction of AE when what the "anti coalition crowd" repeatedly mentioned was the tedium of *actually beating* coalitions and then getting less than a normal war. This kind of history shows a gross neglect of both sides of that argumentative camp alike.