Rana Tahir Mahmood said:
If Muslims depends on "Dua" and everything will be ok then, I am afraid nothing will change the destiny of MUSLIMS.
What made you think that whoever is doing "Dua" is not doing other good deeds to please Allah? I hope that you would be well aware of the fact that Even if we are lucky enough to act 100% according to Quran and Sunnah, we still need to do "Dua" for asking Allah to forgive our sins and accept our good deeds.
If we depend on "DUA" then uptil now lot of Duas were prayed by the Imam-Kaaba for release of Philistine from Israel and nothing happened but it is going worse than ever.
Our beloved Prophet (pbuh) said:
“The dua’ of any one of you will be answered so long as he does not seek to hasten it, and does not say, ‘I made dua’ but I had no answer.’” [Sahih Al Bukhari: Book 75: hadith # 352]
Imam Ibn Hajar (May Allah bless him) writes about above Hadith:
Every supplicant is answered. However, the answer will come in different ways. Sometimes it comes precisely as requested and sometimes by way of something else instead.
[Fath ul-Bari: Vol 11: Page 95]