I know it seems that the God of the OT and the God of the NT are so different, but they really are not. The big difference is that in the OT there was a sin barrier between us and Him. We could not cross it and live and He could not cross it, for He is perfect and can not be in the presence of sin.
So the only way He could communicate to us was with the law and through the prophets. We could not KNOW Him as He really is, we could only know Him through rules and rituals. And no matter how much we did, we could still never cross that sin barrier that seperated us from Him.
Yet, He had a plan. He orchastrated events so that His plan was fulfilled, and His Son was born.
Then Jesus came, fulfilled all the requirements to redeem us from the curse of sin, and the sin barrier was breached! Now we can come directly to Him, through Jesus. Now we can KNOW Him beyond the law, and through Grace. Now we can see the "softer" side, the side of mercy, grace, and love. These are sides of him that we could not see from the other side of the sin barrier, but are very noticeable from this side.
And though there is still a sin barrier in the world, there is now a way to cross it, and that way is Jesus.
I was explaining this to my children one day and thought of it this way. If you could only know someone from a distance, say China, you would only know them from their words or the reports of others. If they were your mentor or "boss" they would have to send you a written list of rules and regulations to follow as a way to "train" you or teach you to be more like he wanted you to be, how you needed to be to be your best.
However, if you ever met that someone in person, and that person was then KNOWN by you personally, you would begin to see a new facet that you had never known before.
What we must remember is that even though we know Him by His love and mercy of the NT, He is STILL the same God of the OT that requires justice, obedience, and humility as well as one that dispenses judgement when necessary; it is now just tempered with mercy and grace for His children.
As for the OT "heroes", I think we tend to forget that they were just human, like us. And they were not perfect, they made mistakes, and they had flaws. We are no different than them. And I am quite sure that if someone were to write my story and read it thousands of years later, it would seem as strange as some of the OT stories. They lived in a different culture, a different time. Things that seem absurd to us now were normal to them. Things that seem common sense to us now was unheard of to them. Not to mention that the stories only highlight the real lives and circumstances of the people. One can assume they really understand what was happening, but you can't really know without being there.
It is a lot like reading a news report today, so much is left out, tiny details that would affect your perception of what was really happening. This is MUCH more true about a writing from a different culture, a different time, written in a different language and translated into ours, and then passed from generation to generation. Though the Bible is accurate in facts, it is also scarce in minor details that would explain all the choices made by them. For, if it contained all the minor details that lead to all the decisions being made, we would never be able to contain them in a book. Thus, only the main content was recorded that had important information that needed to be relayed that explained their history. So, we must be careful about making assumptions about our Bible "Heroes", and then keeping in mind that they were only human.
When you take all that into account, it opens a whole other dimention to the Bible.
Anyways, I have probably muddled up this post. I hope I did at least get the jist of my ideas across. Sometimes OL communicating is just not easy to get it all understood.