The other way to see it is that the employer pays out 15% than he knows the employee will accept for his work (i.e. his net pay). If the employer suddenly doesn't have to pay this, it's gravy, and you're assuming that he'll see it in his best interest to pass that gravy on to the employee rather than apply it to his bottom line and benefit his shareholders. I think, based on my interactions with the real world, that this is delusional.
From a policy perspective, I don't care at what ratio the employer passes that additional "savings" to employees v shareholders. In either case, it's going to people who are actively working to create economic activity, either through their labor or by risking their capital. Beats the hell out of letting faceless bureaucrats give it to deadbeats who do nothing.