Farage's poster was wrong in my view because it sought to wrongly equate the EU freedom of movement problems with the Europe/Middle East/Africa migration crisis. He should have stuck to the much wider issues of free movement rights across the whole EU and the problems that has caused. The population of the other EU27 countries is about 450m so that clearly dwarfs the numbers that have entered Europe as asylum seekers/economic migrants over the last few years. A far bigger potential impact would be Turkey joining the EU.
The EU has been slow to react and agree how to manage the migration crisis, but, to be fair, it has been a huge crisis in Europe's recent history. That does not mean however that it cannot be resolved, so to say that "The EU has failed us all" is perhaps a bit premature. If the EU did not exist at all, this would not stop huge numbers of people trying to flee wars and persecution and getting to Europe and to whichever country they are trying to get to.
Merkel's opening of Germany was a German government, not EU, decision and was highly controversial particularly if she did not consult or get agreement from the rest of the EU. She has suffered somewhat, politically, as a result. On the other hand, Greece can neither control its borders, because of its geography, nor has the resources to cope with the huge number of migrants it has received - some Europe-wide assistance/approach therefore seems the sensible solution.
All in all, I think the poster was scaremongering, designed to fuel people's fear of immigration and foreigners, especially those of middle-eastern appearance. It's a low blow to make political capital out of people fleeing wars and persecution and also to try to criminalise such people.