That must be really, really hard!
It's not something I've had to deal with much - DS does get aggressive at times, but it's not such a consistent thing. If he throws something or bangs it, then he loses it. I think it's more effective if there's a clear link between teh behaviour and the consequence. If he hits me or someone else, then play time is over and he has to do his own thing - I won't do thiings with him if he acts like that.
I suspect your problem is a bit more tricky than that though. Did this start when your DH started working so much? It may well be an expression of her need for more time with him and/or more general frustration at things being different.
If her language is good, the toy thing might work. But it's a modifieid punishment/reward type scenario so doesn't get at the underlying issues here. And there is some reason for this behaviour, I'm sure. Also, if she decides to forego the toys... what then?
Sorry, I don't really have a practical solution to offer you FWIW, I don't think it's harsh, you're dealing with a very difficult situation. And you're right to not just let violence go.