Hi Justin,
A workaround to your problem can be using multiple workflows to get to the required result (messy but doable.)
1) Create a property on the company object just to contain Yes/No as a trigger value (for example “Update Deals trigger”).
2) Have a deal workflow that triggers when it’s Create Date is known. Within that deal based workflow, set the “Update Deals trigger” company trigger property to “Yes”.
3) Create a temporary field on the deal to catch the company’s property value (for example “Temp Company Value”.) This temp field can be updated on all deals without affecting data integrity.
4) Make a company based workflow that triggers (and retriggers) when “Update Deals trigger” is marked as “Yes”. Within the workflow, copy the desired company property into the “Temp Company Value” property of all the related deals (seeing that is the issue which does not yet have a workaround.) After copying that company value into all deals, make sure the workflow clears the "Update Deals trigger" field on the company record (so the workflow can be retriggered for future deals.)
5) Make a third workflow that is again deal based which only updates the relevant deal property (for example “Company Value”) where that deal property (“Company Value”) is unknown and the deal’s “Temp Company Value” IS known. In that scenario copy, “Temp Company Value” into “Company Value” on the specific deal object and then clear the “Temp Company Value” on that deal (if you want, but that is not really necessary, because that property will never again have any relevancy for that particular deal.) In this way, only the latest deal, which was never given a value before, will copy the company’s present value which will be contained in its temp property to the deal property that you really want to be updated.