I often suggest waiting to buy an ETF until it has proven itself, but I don't think that necessarily applies here. DWA has proven, long before launching its first ETF, that it knows what it is doing. Whether PIE would serve as a proxy in your portfolio for broad-based emerging market exposure boils down, I think, to whether you think a product like this should be rebalanced more than four times a year.
You could argue that it's not in your interest to put arbitrary restrictions on a manager in whom you have faith and are willing to pay.
To be candid, there is no correct answer.