This is a good allocation, 60% equities, (30% US equities (VTI); 15% Global ex-US equities (VXUS); 15% Europe (VGK), (but why no specific allocation to emerging market equities? ); 10% property, evenly split between US and other.; then 30% fixed income.
However, if you have 15 - 20 years to go, why are you investing so much of your portfolio in fixed income, i.e. bonds? I know Malkiel provides for bonds in his allocations but this is written from a US perspective. Unless you need income why invest so much in bonds? The only reason for doing so, unless you need income, it is that by including such a high allocation to bonds the resultant portfolio meets you personal risk profile. If so ,you should do it, but if not, and you want non-correlated returns and stability, why not look at SL GARS or equivalent, absolute return or non-correlated funds, timber, short term IE state deposits, or, perhaps, keep an eye open for a suitable entry point into commodities? Diversifying your portfolio by including uncorrelated assets is your only free lunch.
[[Disclaimer: The above is comment / observation and is not a recommendation to follow any particular investment strategy or to buy / not buy any particular fund or stock.]