Jumping back to the tech rehearsal thing. I agree with Aurelia, that part of it is how a director frames it, and I've called directors out on being insulting to the entire design staff by telling the cast that they just have to suffer through tech and then and I quote "get back to the real work." However, that is the exception in my world.
Also, I know that most of the actors I work with understand enough about the process that they a good with sometimes slow techs. As a designer I've also sat through many a normal rehearsal, waiting while one acting beat is massaged, so that I can then see the timing of the next moment in order to build a sound cue that correct. Everyone has to wait at some point.
Beyond this, in my professional work I often only get one 10 of 12 rehearsal, and if I am lucky 2 of them to do all of my work. The cast will have 2 to 3 weeks of rehearsals. Also, the deal that I am making with the director, and hopefully that the entire design staff is making, is that if the show can be given to us for one or two tech rehearsals for us to do our work, then we will give it back at the end of that. I do see some designers who never do the second half of that, once they are involved, they drag their process out across all of the dress rehearsals and previews, and that isn't fair either.