Actually this 50% off voucher Dominos has at the moment will save you an extra 30% off the price you would usually get with the typical vouchers they issue. :)
2 x traditional range pizzas for $18.44 delivered vs. $25.90
We usually order 2 pizzas from the traditional range as my favourite is the Peri Peri beef and my boyfriend always goes for the Godfather one. :) As we only order two pizzas and not three, the best discount we could typically get on these is with Dominos "Traditional range pizzas for $12.95 each delivered", dropping the total to $25.90 from the original price of $36.90. Applying the "50% Off Whole Order Menu Price" voucher on the other hand would give us the same two pizzas for just $18.44. Unfortunately you can't stack vouchers at Dominos (or at least not these two).
That's an extra $7.50 off, which effectively works out at 30% off the usual discounted price. :)
Voucher is valid in Sydney metro for sure, and it expires on the 10th of February.