When it comes to the Imperial Guard, I alway love mixed regiments. I mean, the Imperium is already a very culturally diverse nation. Now if you put individuals from two or more different planets together and have them work together for an extended period of time, I can see a lot of interesting interactions going on.
Not quite suicidal. Death Korps punish the officers who rune excessive casualties with little to no gain. As what happened in the Vraksian siege where many Company commanders were sent to penal legions for sacrificing their companies with little gain. It is better to describe the Death Korps as very willing to sacrifice men if it means to take ground and hold it.
Likewise, that's what Commissars are for. In other regiments Commissars are there to keep a high standard for morale and discipline, but in the Death Korps they are there to act as moderators to help commanders make more rational choices when committing their troops to battle.