The dilemma here is that to test human animals directly may cause harm so testing is done on animals first to determine the effects.

Yes, and then the results have to be tossed the majority of the time because animals have different dna, different manifestations of disease, and different results.

Physician's Commitee For Responsible Medicine

Pharmacology and medical science would not be where they are today without testing animals.

This is also true - medicine would likely be much further. There's likely any number of medicines that haven't made it through animal testing that would help people. A good example is the polio vaccine. The one developed in 1934 used animal testing and was deadly. The one developed in 1947 used cadavers and human testing, and epidemiological studies, and was successful, which is why we've basically eradicated polio in the US.

Animal Testing Limiting Science

However, is it done humanely, is it done for the "greater good", is it justifiable, the question will always test our moral and ethical judgement especially, when it comes to testing products such as cosmetics etc.

It is not humane, and I'm not even going to bother citing sources here because there are far too many. It's not for the greater good, it's not justifiable, and frankly, it's not sensible. There's a quote in Singer's book that points out it takes roughly 4 million dollars, 800 animals, and 5 years to test a drug with a 10% accuracy rate. For the same budget, no animals, and 1 week, 350 drugs can be tested using alternative methods, with 90% accuracy. Pharmagene Labs is already using only alternative methods, and the EU has already greatly reduced animal experimentation, so it can be done.