The current class fantasy is just out of place for the warlocks, and it heavily affects gameplay desing.
Ok simple example.
Why destruction warlock, caster who dedicated his or her life for improving his skills in fel casting, learning chaos magic, is able to instantly summon infernal, that is not only deal baseline massive AoE damage, but also generates resources for the destro.
While demonology warlock, spend time to summon Tyrant, whom not only deals less damage baseline then Infernal, requires to be summoned the last, in order to prolong lifespan of other demons, and also requires additional talents to be viable, not to mention that demonology warlock is not able to directly control that demon…demo warlock can’t control demons, Really?
Destro and affli improves their skills with talents and passives, but why demonology doesn’t improves damage of his or her main demon? Yes demo has mastery that increases damage of demons, but so does destro and affli.