Larian's other games used a different rule system, which would make unlimited summons unbalanced. You cannot use those different-rule-using games as evidence that necromancy is going to be bad in this game because they use different rule systems.
With Necromancers and Warlocks being my 2 favorite classes, I understand your concerns. But I'm going to give Larian the benefit of doubt, and wait and see. As for short rests, they did say somewhere, that between combats would be short rests. If they screw up short rests, it would wreck not only Warlocks but Sorcerers as well. I'm more concerned with reactions, as in the Shield Spell. How's that going to work?
Reactions are likely going to be something you set on your turn, probably a menu where you can select what reaction you'd like to hold, such as "Shield" or "Featherfall" or "Counterspell". On your turn, if the condition is met, the reaction happens automatically.
