"feeling that a world in conflict would be a better crucible for heroes fit to stand against the end"

Moruzond sends his dragons to the dark portal against Medivh and to the Culling of Stratholme to ensure Nozdormu sends heroes there to ENSURE that those events happen. We talked about figures being enlightened here so what if Medivh and Arthas were stopped?

For Medivh there would have been no orcs in Azeroth and no first or second war. Point is there would be no conflict in our world as it is now. Clearly I'm not 100% on the lore here but if I'm correct then Medivh was the Guardian of Tirisfal and so was supposed to protect the world after Aegwynn. Bringing orcs to destroy the world is not something a protector does and if left to his own, it may have been possible Medivh would have come to his senses to save the world, as he appears to try to do in the third war.

Same could be said for Arthas. He was a paladin of the Light. A protector of the innocent. This, though, can be boiled down to him making a poor choice in a crisis. He was not given the help of the people he relied on most and made a snap call against a demon bent on destruction. Assume however Moruzond manipulated things as you will but imagine if Arthas kept the guiding hand of Uther and the support of Jaina. He would have found what we would see as a more peaceful and Light oriented solution instead of killing everyone on sight and becoming hellbent on revenge. But because that never happened, Arthas became the Lich King and was another being to cause conflict and actually helped the adventuring heroes of Azeroth become stronger through all our time in Northrend.

We can extend this to interfering with the escape of Thrall. Thrall needs out and can the machinations of one girl really get past the fortress protecting Thrall? No. A group of adventurers needs to be assembled by Nozdormu to break into Durnholde and let him out. Thrall would then assemble the orcs for the third war and essentially all of the story since WoW's launch. We needed Thrall to also go to Outland and talk to Garrosh so he would become eventually Warchief and lead us to the conflict we're in right now. It all starts when Thrall becomes free. Otherwise he would continue to be another slave and eventually die for the entertainment of Blackmoore.

Since I'm now going off like this, I believe the reason we DON'T see the Infinites anytime we see the Legion is that is as much a threat to Azeroth as the Old Gods. We have been lead there, even perhaps serendipitously, with the other events we have traveled in along our journeys through time. We release Thrall, a key figure in the fight against Archimonde. We go through End Time if only to go to the Well of Eternity. We ensure conflict by saving the world from destruction. Moruzond just wants to create conflict to cultivate heroes, not destroy everything. The Legion had a chance at that at Hyjal and the Well of Eternity until heroes sent by Nozdormu went to that point in time to protect Azeroth. This gives the world more time to create stronger heroes to remove the Old Gods perhaps or even to vanquish the Legion and Sargeras himself.