[Tyrius]

Have you played 5th edition or with screamers? Str 8 melta vs 10 rear armor on almost every vehicle but a land raider is almost a guaranteed dead vehicle. They are not pricey and will always get back their points if they kill one vehicle. Yes they cant do it the first turn but they are the best option for taking out vehicles and the cheapest way to fulfill the tank hunting role that demons have few options of taking. You say "if" someone has vehicles. After 5th edition almost every competitive army outside of tyranids will be taking them. Screamers are also the fastest unit the demons have which is also good for last turn contesting of objectives. Its a good biased opinion of the demons codex, but it seems your theoryhammer is far more then your playtesting with almost every option you named.