Horde did all they could to save Azeroth for two last expansion. As always, Alliance attacked them in the most dire time. Horde leadership, however, for some reasons wants to stand by while their subjects are slaughtered by Alliance forces.
This is clear sign of your ignorance. Sylvanas legally claimed her title when Warchief Geya'rah sworn loyalty to her.Your logic is painful. If Vol'jin is an usurper then Sylvanas who got made Warchief BY HIM is obviously not legitimate either... but I guess everything goes in defending her.
Magatha's disregard of rituals shows how practical person she is. Mak'gora is the way to choose the strongest for the Warchief but there are other ways to maintain the strength. Warchief Orgrim(in original story) claimed his power by silent assassination of previous Warchief. He knew that honor is secondary value after survival, the reason Horde was created.Don't worry you will be back to slaughtering innocents soon enough and Baine will again not do anything for halve an expansion cycle. It is funny how you want to have someone lead that spits on the core ideals of the Horde and goes as far as to manipulate one of the most important rituals you folks have for personal power. Basically it shows that you do not care one bit about the Horde, you just want to be evuul, no matter on which side and for whom you gotta work.
The expansion starts with Gul'dan imprisoned, so we know that it was after war with Draenei started. In main universe Horde started the war without fel power too. They had reasons to believe that Draenei are planning an invasion against them so they did a couple of preemptive strikes.Oh the Draenei still got plenty genocided in WoD, most of their cities were destroyed with Shadowmoon Valley remaining as the last bastion. The only difference is that this time we managed to jump in before the Orcs could finish them and that the Orcs did not require demonic corruption to go on mindless killing sprees, they just do it because of the fun of slaughtering innocents.
As we can see, although Velen didn't plan an invasion, other Draenei are more than happy to kill.